|“||Stefan. You know I always wondered what it would be like to be loved by you. You've got to admit for that one moment your feelings were real. This truly has been the role of a lifetime. Stefan, I love you, I've always loved you.||”|
Katherine fell in love with Stefan when she met him in Mystic Falls in 1864. Although she was also seeing Damon, she had a clear preference for Stefan. She secretly watched over him while running from Klaus. Katherine was unwilling to put her love for Stefan above her own survival and when she returned, they became enemies, as Katherine wanted to deliver Elena to Klaus in exchange for her freedom and Stefan was in a relationship with her at the time.
Dead Man on Campus marked the formation of a positive relationship between Katherine and Stefan. Katherine helped Stefan deal with his traumatism from being locked away and repeatedly drowned to death by Silas for three months, and then he saved her from killing herself by catching her as she was about to hit the ground after jumping from the top of a clocktower. In The Cell, Stefan was still watching on Katherine so she did not commit suicide.Later, the two of them are locked together in a cell by Caroline as part of an experiment to try and help Stefan deal with his traumatism from being locked away. Katherine managed to make Stefan overcome the traumatism by telling him that the real problem wasn't how he felt about being trapped, but rather the pain he felt from Elena leaving him and being with his brother Damon. They almost kissed but before they can Caroline opened up the safe, worried because they had gone silent. Later, when Caroline wasn't watching them anymore, they kissed each other that progressed into sleeping together.
Given their night together, Katherine's love for Stefan was revived and she was inspired to live with a hope of being with him whether she died or not. A sentiment Stefan didn't seem to share, seeing it as a one-night stand with no other complications since he could not fully forgive her for all the torment she unleashed on him ever since 1864. However, as Katherine was spending her last day "alive", Stefan showed a surprising amount of compassion for her and admitted that he not only didn't hate her but he wanted her to find peace and happiness after her harsh life and things weren't her fault. He furthered this by going inside Katherine's head in her last moments and gave her visions of erasing her family's murder and having her hold her baby.
Stefan and Katherine may be a part of The Doppelgänger Prophecy. ''They are known as "Steferine" and "Sterine" by fans.
Early HistoryIn Katherine's flashback to 1864, she admitted that she saw Stefan for the first time before they officially met in Salvatore Mansion. While she & her maiden were on their way to Lockwood family, her driver stopped to see if Stefan needed assistance with his busted carriage. Katherine spotted him & since then she changed her plans. Stefan met Katherine Pierce for the first time when she arrived in a carriage with her maid and witch, Emily Bennett. Stefan's father; Giuseppe Salvatore had offered Katherine to stay with them as she had supposedly lost her family in a fire.
There was immediate chemistry between the two. Back then Stefan was shy brother & Damon was the one, who first started to compete of Katherine's affection. Soon after that Damon left Mystic Falls a soldier & went for a war. It was a moment, when Stefan started develop feelings for Katherine & they become closer. Later, Stefan escorted her to the Founder's Ball, when afterwards he told her that he loved her. She was astonished by this, and appears to be left speechless by his kiss.</span>
Soon afterwards, while Stefan and Katherine were having sex, she reveals to him that she is a vampire. He is not accepting of this and appears to be very frightened of her. Katherine, not wanting to lose his love, takes his fear away through compulsion. She also compels him not to tell anyone.
On the night that Katherine was taken away during the round up of the 27 vampires, the last person she was with had been Stefan. Giuseppe spiked his drink with vervain, which poisoned Katherine when she fed on him.
Stefan and Damon tried to save her, unknowing that she had a plan to escape. While carrying her out of the carriage the vampires were trapped in, they are both shot, having Katherine's blood in their system. Katherine had been compelling Stefan to drink her blood for weeks. Stefan, Katherine and Damon all lie next to each other, dying. Stefan turns to Katherine, and in his last few moments alive, she says "I love you, Stefan." He then dies.
Katherine is put back inside the carriage, but is then helped to escape by George Lockwood in exchange for the Moonstone. She is prepared to leave, but sees Stefan and Damon's lifeless bodies on the ground. Ignoring Damon, she runs to Stefan, caressing his face, proceeding to say "I love you, Stefan. We will be together again. I promise." She then kisses him for the last time and leaves him, not seeing him again for another 145 years.
Weeks after Stefan was newly turned and still lacked control of his bloodlust, he went on a rampage, killing members of the Founding Families for what they had done to Katherine.
Throughout The Vampire Diaries Series
In You're Undead to Me, Stefan described Elena his thoughts about Katherine: "So let's start with Katherine. She was the most beautiful girl I had ever met. She had this perfect olive skin. And she had this laugh; it was ridiculous, her laugh made you laugh. And she was fun, she knew how to have a good time but Katherine was also very impatient and entitled and selfish and impulsive. Enter Damon. He claims that he was with her first. I don't know. I do know I did some things that I'm not proud of and my biggest regret is not being able to make it right before she died. I miss her, but I'm no longer crippled by her loss."
In History Repeating, Stefan confessed, that he believes his feelings for Katherine were fake: "It wasn't real, Damon. Our love for Katherine. She compelled us. We didn't have a choice. Took me years to sort that out,to truly understand what she did to us."
In The Turning Point, Stefan asked by Elena, described his room: "It's the only place that has remained constant. This room holds every memory that i ever thought was important enough to hold on to." Later, when he leaves Elena to get her some water, she finds in his room a picture of Katherine.
In Bloodlines, despite the fact that Stefan completely denied his feelings for Katherine, he admitted that Elena's resemblance to Katherine caught his attention: "When I pulled you out, I looked at your face. You looked like Katherine. I couldn't believe the resemblance. After that, I spent months making sure that you weren't her. I watched you. I learned everything that I could about you. And I saw that you were nothing like Katherine. And I wanted to leave town, but, Elena, I couldn't."Katherine makes her first non-flashback appearance in Founder's Day. She approaches Elena's house, so far the viewers believing it to be Elena. She talks to and kisses Damon, Damon also unknowing that it is Katherine. She is invited in by Jenna. She talks to John Gilbert, then proceeds to cut of his fingers because of his ring. He realizes that it is Katherine, and she stabs him. Elena walks into the house, heading towards the kitchen after hearing a noise, while Katherine waits for her.
In The Return, Everyone is shocked when Katherine returns to Mystic Falls and causes trouble. When Stefan hears someone enter the Gilberts' house, he runs downstairs to find Katherine. The second she tried to kiss him, pretending she was Elena coming home from seeing Caroline the night of accident, he'd known it was her. He threw her across the room. They thrust each other from wall to wall until Stefan is distracted by the sound of someone approaching the front door. This allows Katherine to twist his arm 'til he's down on the floor in pain. She ran away, just before Damon and the real Elena enter.
Next day in Lockwood Mansion Stefan meets Katherine again - she invites him for a walk. Stefan just wants to know why she's there. Katherine says maybe she missed him. He wants to know her game so he'll know what rules to play by. Katherine smiles. "No rules, Stefan. Don't you remember? No rules." She walks off and beckons him to follow her outside. Katherine spoke a lot on her walk with Stefan. She repeatedly looked Stefan up and down, noting that he was stronger, meaner, and sexy, and that she was hurt he'd fallen in love with someone else. He told her he wasn't Damon, who obsessed over her for 145 years. He said he never loved her, she had just compelled him to.
"Believe what you want, Stefan. But I know the truth and deep down so do you." She said. "Well the truth is you're the same lying, selfish manipulative bitch that you've always been. So whatever it is that brought you here, why don't you just get on with it and leave town. Because if you don't, I will hunt you down and I will rip your heart out. Stefan said. Katherine then told him she came back for him and Stefan said the problem was that he hated her. She grabbed the candle stand and stabbed him in the stomach with it. "You hate me, huh? That sounds like the beginning of a love story, Stefan. Not the end of one." She said. Katherine would soon after admit to Damon when they almost had sex that she had never loved him the way he wanted her to. It was always Stefan.In Memory Lane, Katherine goes to the Boarding House to spend some time with Stefan. She gets an early start by manipulating his dreams, bringing him back to when he had escorted her to the Founder's Ball in 1864. In the dream, he notices that Damon has found someone to entertain himself with - Elena. Katherine then takes the dream to present day, where Elena and Damon are getting cozy at the Mystic Grill. Stefan wakes suddenly to find Elena asleep in his arms, but he quickly realizes it is actually Katherine.
He questions her about werewolves. When Katherine asks him why he kept a picture of her from 1864, Stefan does not reply and Katherine tries to kiss him. Stefan manipulates Katherine and, just as she is about to kiss him, stabs her with a vervain dart and takes her down to the basement. He questions her about her motives and why she came back, but Katherine repeatedly states that she came back for him. She insists that she never compelled Stefan to love her, that his love for her was real, and she only compelled him not to fear her. In a final flashback to 1864, Katherine is ready to leave Mystic Falls, but falls back to kiss an unconscious Stefan one last time, promising they would be together again one day.
In Masquerade, Katherine dances with Stefan and briefly tries for a diplomatic surrender, but when he refuses to give up the moonstone, she kills Aimee Bradley in the middle of the dance floor. Later in the episode, when Katherine was trapped in the same room with Salvatore Brothers, she lets Stefan know she has stalked him over the years, including 1987, when he went to a Bon Jovi concert, with his best friend Lexi. When he demands to know, what Katherine has been running from, she just mouths "I love you," at him.In By the Light of the Moon, Katherine and Stefan are stuck in the tomb together. Katherine toys with Stefan's mind while he is sleeping, and gives him a dream in which they had sex. Stefan wakes up very angry. She repeatedly states that she genuinely loves Stefan; later she does offer the useful advice of seeking out Isobel for information about Klaus. She gets out of the tomb after Elijah is killed and his compulsion wears off. In the deleted scene for this episode Katherine has a dream, that Stefan and her share a conversation, in which he seems to show feelings for her. However, it's implied to have simply been a trick of his when he attacked her it as a form of revenge for what Katherine had did to him. When she wakes up, Stefan told her that if she stayed out of his head then he'd stay out of hers.
In The House Guest, Katherine is freed from the tomb and decides to help them against Klaus. Damon was suspicious of her intentions and demanded to know why she was really helping them instead of leaving town. Eventually, Katherine admitted to him that she was forced to make a deal with John Gilbert and Isobel when she was trapped. If she didn't stay to help them against Klaus, then they would kill one of the Salvatore brothers due to their desire to keep them out of Elena's lives. Katherine could only save one of them so she choose to save Stefan over Damon.
In As I Lay Dying, Stefan comes to Alaric's apartment, where Katherine is being kept, and she asks him why Klaus isn't dead and why she isn't free. When Katherine hears Klaus approaching, she hides Stefan and tells him to be quiet, but realizes there is no use and steps out to see Klaus with him.
In The End of The Affair, it was revealed that in the 1920s, Katherine was in Chicago at the same time as Stefan, but she only observed him from afar. After a police raid cleared out the speakeasy, Katherine spotted Rebekah's necklace on the ground. She moved to pick it up, but ran away before Stefan could see or notice her. She watched him for a few moments before slipping into the shadows.
In Disturbing Behavior, Katherine meets Stefan in Chicago when he steps outside a shop for a moment. Stefan warns Katherine that Klaus will kill her if he finds her here. Katherine believes Stefan is up to something and wants him to tell her. Stefan tells Katherine that they don't know where Elena's necklace is and that he has to keep Klaus and Rebekah from finding that out. Katherine warns Stefan that Klaus is smarter than him, stating that he is 'smarter than everyone.' Later in the episode, Katherine saves Stefan from Gloria by stabbing her in the neck. Katherine guesses Stefan's plan, and tells him that if he is planning on making a move against Klaus, she wants in. Stefan tells her that it's good to want things, and leaves.
In Homecoming, Stefan and Katherine plan, together, to stop Damon from killing Klaus so he won't die along with Klaus. Katherine manages to get through to Stefan's humanity, convincing him to help her stop Damon so he won't die. She seems to be one of the only people to bring out his humanity this season. Katherine reveals that she was also trying to save Stefan's life, along with his humanity. She tells him that she likes the 'old him' better, and that she cares for other people besides herself. She tells him she loves him, and that she loved Damon too.
In We All Go a Little Mad Sometimes, Katherine appears as Elena's hallucination. She torments Elena & tells her that Stefan will hate her as vampire - just as he start to hate Katherine after the truth of her identity came out.
In Bring It On, Katherine is mentioned by Stefan in his conversation with Elena. He compares her to Katherine, saying that Katherine used her body to manipulate people.
In Because the Night Damon is searching for files about Katherine's whereabouts while talking to Stefan on the phone, Damon mentions that It goes by birthdays and he can't remember Katherine's. While on the other hand Stefan tells Damon her birthday is June 5, 1473.
In American Gothic, Damon and Stefan arrive in Willoughby, PA. At the café, Katherine and Rebekah bicker and Rebekah twists and breaks Katherine's wrist, but they are interrupted when Damon and Stefan approach. When they question the two on Elena's whereabouts, Katherine replies that Elena is probably in the town morgue by now. Looking satisfied with herself, Katherine reveals that Elena unknowingly went to meet Elijah and he probably killed her immediately after realizing she was not Katherine. Stefan questions Elijah & Katherine's relationship, he instantly knows that Katherine just used Elijah as tool to make a deal with Klaus & get her freedom back. Later, he leaves in search of Elijah and Elena. He uses Katherine's phone to call Elijah, who demands Katherine be kept safe.
In The Walking Dead Elena tries to kill Katherine and almost succeeds before Stefan comes and saves her to which Katherine replies "Thanks for the save, handsome". Elena becomes furious and considers the fact that Stefan still may have feelings for Katherine which is why he won't let her die.
In I Know What You Did Last Summer, while she is taking a bath in Damon's tub, Silas imitating Stefan shows up suddenly, they flirt - thinking it's Stefan, she offered him a shared bath and when they are about to kiss Silas grabs her neck, attempting to drown her.In Original Sin, Katherine decides to accompany Damon and Elena in search of Stefan, after having the same dream as Elena with the possible whereabouts of Stefan. She says that Stefan is also important to her and she jokes in all the way to Damon and Elena about their relationship.
Later in this episode, the secret about doppelgängers is revealed. According to Qetsiyah, the doppelgängers of Silas and Amara have been supernaturally brought together repeatedly, by destiny and the Universe. She has seen them all finding each other and falling in love with each other, century after century. Despite nature's great hatred for immortality, it appears the doppelgängers continued to live the life that the immortal Silas and Amara couldn't have.
In Dead Man on Campus, both Damon and Stefan are invited to Caroline and Elena's college party. Despite killing Silas, Stefan is still suffering from the memories of being locked inside the safe. He refuses to go to the party. Katherine meets Stefan at Mystic Grill. Katherine is drunk, feeling hopeless about the fact that she is dying. They have a conversation. Katherine tells Stefan that what he is suffering is called PTSD - Posttraumatic stress disorder. Nadia arrives. Katherine introduces her to Stefan.Later on, outside Mystic Grill, Katherine discovers Stefan getting crazy because of the memories of being locked inside the safe. She calms him down by telling him to remember and name the people he has killed in order, starting with Giuseppe Salvatore. By telling her the names, he can control himself. At the end of the episode, Katherine decides to commit suicide to end her misery by jumping off the bell tower. She writes a note to her daughter Nadia. Before Nadia has a chance to read it, Stefan discovers the note. Katherine jumps off the tower. Stefan catches her right on the moment which she is about to hit the ground. Katherine is surprised. Stefan tells her, "You're Katherine Pierce. Suck it up." Katherine becomes speechless. As Stefan walks away, she smiles.
This episode marks the formation of a positive relationship between Katherine and Stefan. Katherine tells Stefan about her issues and helps him control his emotion. At the end, he saves her life. It can be concluded that they are no longer enemies. They are friends.In The Cell, Stefan was keeping a close eye on Katherine after the suicide attempt. She was writing in a journal at his request because he's worried she will try to kill herself again. But Katherine was just as concerned about him since she overheard some of his PTSD terror. Stefan didn’t want to talk about it, but Katherine had already invited Caroline over to help…terrorize Stefan by putting him back in his box. Needless to say the therapy that Caroline found in a textbook didn’t work. Stefan was still freaking out and Katherine was questioning whether or not Caroline and Stefan had ever hooked up. But then Her loss, Katherine said, because he's great in bed. Stefan was too busy having a panic attack to hear that. In fact, He passed out. "How do you help the guy who always comes to the rescue?" Katherine pointed out that Stefan is the hero of the story and it can’t be himself that he needs to save.
Her solution was to get into the safe with Stefan. He pointed out it was dangerous and she reminded him that she was dying anyway so it didn’t matter if he ate her. Stefan started freaking out and getting upset and Katherine continued to talk his hear. She suggested that what he was really upset about was Damon and Elena and that he wanted to run away and never come back, but he kept finding excuses not to. She believes his trauma is because he’d rather experience the physical pain than the emotional pain.To further prove her point, Katherine exposed her neck to Stefan. He got his vampire face on, but her words were getting through to him. They kept getting closer and closer and it seemed like they were going to kiss and that was when Caroline felt the need to open the box because she thought it was too quiet. Stefan got out of the box and hugged Caroline, but his eyes were on Katherine…
At the Salvatore house, Caroline is trying to move the safe all by herself. She yells for Stefan to help but he’s cleaning up the room he tore up earlier. Katherine goes to see what he’s up to. She helps him straighten up. Stefan tells her that she was right he does need to move on. They kind of drift towards each other. Katherine caresses his chest, unsure of what he’s going to do about it. Stefan kisses her and they start having a pretty sexy scene.
In Fifty Shades of Grayson, Katherine woke up in Stefan's bed with a smirk on her face. She went to cuddle up on the youngest Salvatore when she noticed a grey hair on the sheets. She was aging fast. In a panic, she ordered Stefan not to turn around as she draped herself in a sheet and ran out of the room.Later the same day, Katherine was looking in Stefan's mirror at her wrinkles. "Her chickens had come home to roost in the form of wrinkles." Stefan said. Katherine wanted to talk about their night together, and Stefan quickly shot down her hopes. They got swept up, he said. He wasn't ready to forget everything she'd put him through for the last 147 years. She said that she's dying - this time for real. She showed him her grey hair and was all, "What does someone have to go through to get a little redemption around here?" Stefan seemed more sympathetic, but nonetheless replied "147 is a long time to forgive in one night." She came back: "One night, an eternity... You'd never look at me the way you look at Elena, would you?" He didn't respond. Katherine went to walk away, and Stefan stopped her. He interlaced his fingers with hers. "I'm sorry that you're dying." "Trust me, I am, too." And then she left.
In 500 Years of Solitude, Stefan informed Nadia when she showed up in the hospital, that Katherine wasn't expected to last the day, so he wanted to take her home to Salvatore Mansion to die in peace. Later, increasingly gray-haired Katherine was up in Stefan's bed, instructing him to slit her throat the second she began to sag anywhere and worrying that she saw an age spot. Stefan found her deathbed vanity charming and held her hand. After that,Stefan had come downstairs to chastise everyone for being insensitive enough to celebrate Katherine's death.
Damon told Stefan not to be fooled, and Stefan finally did a shot—but he said he was drinking to Katherine the survivor. Damon blamed that on Stefan having had one night of hot sex with Katherine.
When Katherine was left alone, Liz had brought sedatives to help her with the pain, but Katherine didn't want to take any because they'd make her weak, and that's when Damon could get inside her head. Damon injected her anyway. What he saw was a flashback to Mystic Falls in 1864 that we'd never seen before: Katherine first spotting handsome Stefan when her driver stopped to see if Stefan needed assistance with his busted carriage. Would his family take in a poor orphan girl from Atlanta? Katherine wanted Damon to see how fate had brought the doppelgängers together.
At the end of the episode, Stefan sat down on the bed and told Katherine to close her eyes. He was there to say goodbye. She said she wanted to see him. He said she would. He touched her face and saw the memory of her finding her family dead. She said Damon told her she deserved everything bad that had happened to her, and he was right - she didn't deserve to be loved.Stefan asked her to open her mind to him. He took her murdered family and the blood out of the scene. He told her none of it was her fault. She was just a 17-year-old girl. We heard a baby cry. Katherine was crying, and if you looked at Stefan, he was fighting back tears. Katherine went to the crib, which had her baby in it, and a bright light shined up at Katherine's face. Stefan kissed her forehead. "Goodbye, Katherine," he said.
In The Devil Inside, after Katherine taking permanent control of Elena's body, Nadia was ready to leave town, but Katherine wasn't. For the first time, no one's after her, she said. She told Nadia she could do what she wanted, but she'd like her to stay, too. Nadia knew Katherine wanted something. Katherine said she wants it all: her daughter, her immortality, and Stefan. "He's my one true love." Katherine decided to stay in Mystic Falls to win back Stefan.
In Total Eclipse of the Heart, Katherine happily journaling about her new life as Elena and removing photos of Damon on her cell phone and set a shot of Elena and Stefan as her wallpaper. She is devoted to win Stefan back. She is trying to find a way to make his way closer to him and when Stefan calls her and wants to talk, she invites him to the Bitter Ball.At the Bitter Ball, Katherine instantly got Stefan on the dance floor and told him she was happy she was done with Damon. She'd tried to fix him, but he'd changed her, and she wasn't sure she liked who she was now. Did Stefan like her or miss the old her? - she asked.
At the end of the day Katherine asked Stefan to get the splinter out of her back, which he did. She guessed what he'd tried to tell her earlier - Aaron was dead and Damon had done it.
Katherine wondered why he wasn't honest with her to begin with. She asked him to be honest with her. Stefan replied that ever since he'd noticed Elena falling for Damon, he'd been waiting for Damon to screw up so badly that she'd turn on him. But when it didn't happen, he stopped waiting for Damon to fail because he liked the person he had become,and he doesn't want to lose that person. Katherine said she'd help save Damon not for herself, not for him but for Stefan.In No Exit, Stefan was helping "Elena" study for a history test. Katherine caught herself disagreeing with the textbook but covered well by saying she'd written a paper about the Holy Roman Empire in high school. They were interrupted when Caroline arrived with files from her mother, Sheriff Forbes, confirming Damon's bloody trail. Stefan felt guilty letting him go after Wes once he realized Damon's now feeding on vamps. Katherine went off with Stefan to look for Damon.
At a gas station, "Elena" and Stefan recapped where they stand on Damon's redemption: Stefan is holding out hope; she is only there for Stefan because she can't handle the rollercoaster of caring about Damon. When Stefan went inside to get them something to eat, Katherine broke something in his car. When Stefan discovered his car was broken, Katherine took the opportunity to ruin her shirt and get grease all over herself - so she could suggest they get a hotel room while they wait for the car to be fixed. Stefan resisted, but Katherine gets what Katherine wants.At the hotel, Katherine attempted to get Stefan drunk while he told her how tough it could for a man to love her and lose her. Their hands touched when she reached for his glass, and he suddenly had to go wash up. Later, Stefan's car was ready, but Katherine was in no hurry to leave. She asked Stefan to grab her a shirt, and then she left the bathroom door open as she played with her hair longer than any woman would. She dropped her towel and lowered the shirt over her torso with her back to Stefan, who was watching. Fully clothed, she walked up behind him, ran her hand up his arm, and then kissed him. Stefan broke off the kiss, saying it was wrong because she and Damon just broke up. He went to get the car and she smirked and called Nadia.
Katherine and Stefan arrived at the house to find Damon moping, blood still on his mouth. He begged them to leave, but Stefan said he wasn't afraid of him. He was, however, smart enough not to come inside, but Katherine saw an opportunity. She wasn't afraid of him either, she said. In she went. Now she couldn't leave. Stefan followed her. Katherine said she'd prove Damon could resist this. She cut her hand. She practically put her hand in Damon's mouth while saying his love for her was stronger than any craving. Damon bit Katherine. She kicked a stake in Stefan's direction, but instead of using it, Stefan cut his wrist to draw Damon's attention. When Damon knelt his head to feed, Stefan snapped his neck.In Gone Girl, Stefan broke the news to Damon about Katherine being a passenger in Elena. They had a plan - Bonnie, with Liv's help, found dying Nadia in the church. In the same time Katherine was looking for Wes to take the cure for her daughter - she found him, presumably killed by Damon in act of revange. Stefan called her to let her know they'd moved Nadia from the church to Salvatore Mansion. Nadia yelled for Katherine to run. Katherine had tears in her eyes.
Katherine stormed in and said she was there to see her daughter. She said to her the last goodbye - Nadia died. "Your mother loves you," Katherine said, with a tear falling down her face. Nadia was there outside her body with tears rolling down her cheeks, too. Nadia took Bonnie's hand, disappeared, and Bonnie cried out. Then it was over.
Katherine stood, faced the crowd, and said this is it. Then she bolted for the door. But Damon was there. Katherine wanted to know who had the knife that would finally kill her. It was Stefan. She told him she'd always loved him and kissed him—and that's when he stabbed her. She died on the floor, leaning back against the couch.In While You Were Sleeping, Elena discovered that Katherine had been writing in her journal. She read about Katherine trying to seduce Stefan in the hotel room and hallucinated her own hot version of it, which ended with her pushing Stefan away and asking why he didn't recognize that it wasn't her sooner.
In Stefan's Diaries
Stefan and Katherine share a similar relationship in the trilogy book series 'Stefan's Diaries,' which follows the TV series. They meet while Stefan is engaged to Rosalyn Cartwright, but the engagement ends when Rosalyn mysteriously dies and she is found dead by Stefan. Katherine is the culprit, though she promises Stefan that she didn't murder Rosalyn. Stefan is informed that Katherine killed Rosalyn by Katherine's handmaiden Emily.
In The Novels
In the books, Stefan and Katherine's story is entirely different. While in Italy they meet, as Katherine was dying from an illness and her father hoped the warmer climate would help Katherine. Katherine must choose a husband if she wants to stay in Italy, but she soon becomes torn between Stefan and his malevolent brother Damon. She makes a decision, goes to them both one night and gives them blood. She reveals her decision but they reject her decision, each wanting her to himself, and Katherine runs away in tears, showing her childishness to both the brothers. Stefan and Damon become angry at each other when Katherine leaves ashes, her dress, and her lapis lazuli ring under her favorite tree and leaves a suicide note. Believing Katherine to be really dead, they fight and kill each other with swords, waking up as vampires. Katherine returns and becomes angry at Stefan and Damon, Stefan especially, for daring to pursue another woman, but is killed by Elena Gilbert when her lapis lazuli necklace is ripped off.
- Katherine saw Stefan for the first time before she met him, because of this first impression she decided to stay in Mystic Falls in Salvatore's mansion.
- Stefan was turned into vampire by Katherine's blood. He & Damon died trying to save Katherine's life.
- Stefan is wearing daylight ring given by Katherine.
- Weeks after he was newly turned, Stefan went on a rampage, killing members of the Founding Families out of revenge for what they had done to Katherine.
- Katherine and Elena have both claimed to love Stefan first.
- Unlike Elena, Katherine has always chosen or preferred Stefan over Damon.
- Katherine admitted, that Stefan is her one true love in The Devil Inside.
- They are both doppelgängers from different bloodlines.
- Katherine in The Cell and Elena in Bring It On have both admitted that Stefan is good in bed.
- Stefan was keeping Katherine's picture since 1864, he also remembered Katherine's birthday (Because the Night).
- Caroline Dries about Stefan & Katherine: "I'm so pro-Stefan and Katherine too and I think it's because they have such deep dark history. I mean she really put him through the ringer and yet there is something about Stefan that softens Katherine. So to see a little shade of vulnerability with her, even just a peek, it feels like you're getting so much satisfaction out of it. He's her Achilles heel and that's what I like about the relationship. And they have such great chemistry between them."