|“||I know we're supposed to be killing her with kindness, but can't I just kill her?||”|
They have known each other since childhood and became close friends many years before Pilot. However, as a human, Caroline was always jealous of Elena, as she felt that all the boys were always attracted towards her friend instead of herself, and that, as a result, she was always the one being left out.
When Caroline became a vampire, she also became less insecure, and much more confident. As a result, their relationship improved and they became even closer friends.
However, their relationship degraded when Elena became a vampire and then broke up with Stefan and started dating Damon instead; Caroline never liked Damon's personality, and was always resentful of him ever since she had become a vampire and had found out about all the times he had compelled her and used her to serve his own interests. Because of this, she obviously disapproved of her friend's and Damon's relationship.
Their relationship further degraded when Damon made Elena turn her humanity off, to the point that they are now enemies: they had a violent fight after Elena tried to hurt Caroline's mother, Liz, and Elena even tried to stake Caroline. Furthermore, in Pictures of You, Elena steals Caroline's prom dress and ruins the prom night that she spent so much time organizing.
Although Elena is angry towards many of the people that she once considered her friends for different reasons, Caroline seems to be the one that she feels the most anger towards.
Since Elena has turned her humanity back on in She's Come Undone, the future of their relationship is uncertain. One could assume that they will be friends again, but it is unknown whether Caroline will forgive Elena for what she did when her humanity was turned off, or whether Elena will be able to forgive herself for trying to kill Caroline twice.
When Elena first returned to Mystic Falls after the accident , Caroline came off as somewhat insensitive towards her. Sometimes, their relationship was friendly, and sometimes competitive with Caroline being the more competitive one, like when Caroline was attracted to Stefan at the Back to school party in 2009. When Stefan rebuffed her in favor of Elena, she was insulted and jealous of Elena. However, as time went on, their relationship improved, with Elena shocked and worried over the car accident that Caroline was in during the Founder's Day celebration. While Elena was opposed to Damon feeding Caroline some of his blood even though she might die, she was relieved when it helped save Caroline's life.
After Katherine turned Caroline(because you need a vampire for the sun and moon curse and she wanted to turn Caroline to Klaus); she also used Caroline as a spy on Stefan and Elena. Damon wanted to kill her, but Elena opposed doing so. Later, when Damon tried to stake Caroline, Elena stepped in between them and so saved her. Although for a while it looked uncertain as if they would remain friends, they opened up to each other more, and thus are likely to stay friends. It seems that when Caroline turned into a vampire, her and Elena can talk more and can't keep secrets from each other.
During the season, Caroline has realized all that has happened in the town and as Elena, Stefan, Bonnie and Alaric have protected Mystic Falls. Caroline does not hesitate when being part of the plan to destroy Katherine.
In The Birthday, Caroline's on the phone with Elena, chatting about Elena's 18th birthday party that is going to happen if Caroline has anything to do with it. Elena is all but enthused, especially when Caroline brings up how Sheriff Forbes came across vampire attacks in Tennessee.
Later on, we see Elena venting to Caroline about her Damon woes as they sort through what appear to be birthday party materials. Every now and then, Tyler throws in his own opinion in response to Elena’s problems, and his blunt attitude is driving Caroline crazy. Elena is in a delicate state and Tyler isn’t being very sympathetic about her situation. Elena gets a call from Bonnie and leaves the room.
Elena’s birthday party is in full swing when Damon and Elena arrive, and Caroline looks as pleased as ever at the turnout. Meanwhile, Elena tries to resist the perkiness that Caroline exudes, but she doesn’t last long. The girls walk off arm in arm into the swarm of party-goers, ready to celebrate. The girls end up in the Stoner Den where they find Matt of all people. He gives Elena a kiss on the cheek and wishes her Happy Birthday, all while completely ignoring Caroline. “He hates me,” Caroline says. “His hatred of me has driven him to drugs.”
On a mission when she comes across Caroline, who has taken a time-out to have a snack and regroup. Caroline seems like she has relaxed a bit until Elena says that she wants to “pass on the whole cake thing.” Caroline is extra passionate about the cake and generally celebrating Elena’s birthday. Caroline: “You have to admit that you’re kinda just letting your life pass you by. And isn’t Stefan the one who wanted to make sure that you lived it?” While Caroline is drunkenly apologizing for how she reacted to Elena’s disinterest in party activities, Elena comes across a bulletin board full of newspaper articles and possible routes that point to where Klaus and Stefan have attacked.
As Damon and Elena develop into a relationship, Caroline doesn't hide her distaste of Damon, who abused her in season 1, or preference to Stefan, who she gets closer to and soon becomes her best friend. Elena and Caroline's stubborness gets the pair into arguments always about how Elena is dating Damon who, in Caroline's view, is still cruel like he was to her when she was a human.
When Bonnie, Caroline and Elena have a sleepover at the Salvatore's, Caroline and Elena get into an argument about how Elena's suddenly believing and trusting Damon. It becomes worse when Elena reveals her relationship with Damon has turned sexual. Then, in her stubborn fury, Caroline blurts out that Elena is sired to Damon. This causes friction and even more so when Caroline keeps reminding Elena that any feelings she might have for Damon could have been caused by the sire bond.
When Jeremy dies, Elena turns her humanity off because she can't deal with the pain. She loses all emotion outside of recklessness and happiness, which puts her at odds with Caroline. When Elena nearly attacks Caroline's mother, Caroline becomes furious and tries to attack her. When they meet up later, they get into a physical fight that ends with Elena almost killing her, but is stopped by the Salvatores'. Though deeply upset, Caroline does not give up on her, yet has a hostile relationship with her afterwards.
- Elena: "What makes you such an expert on who I am?"
- Caroline: "Because we've been friends forever."
- Elena: "I tried to kill you, Caroline. I'm not exactly BFF-material anymore. You should move on."
- Caroline: "I am not going to give up on you."
- They're both vampires now, Caroline turned first in Brave New World, while Elena changed a year after her in Growing Pains.
- Damon Salvatore's vampire blood was in their system when they were both killed by Katherine and Rebekah, respectively.
- They were best friends for many years before becoming enemies.
- Although they are also best friends with Bonnie Bennett, they are both also best friends with one of the Salvatore's brothers: Elena is also best friends with Damon Salvatore and Caroline is also best friends with Stefan Salvatore.
- They eventually become enemies like in the novels, though for completely different reasons.
- They both slept with Matt Donovan and Damon Salvatore. Matt is Elena and Caroline's ex-boyfriend. Damon is Elena's boyfriend and Caroline's ex-boyfriend.
- They both had three on-screen relationships.
- Caroline was with Damon, Matt and Tyler. And Elena was with Matt, Stefan and Damon.