The mother-daughter relationship between the witch, Bonnie Bennett, and the former-witch-turned-vampire, Abby Bennett Wilson. Their relationship was basically nonexistent being Abby abandoned her as a child. However, they reconnected when Stefan Salvatore asked Bonnie to locate her mother. Bonnie only did it for her friends and to track down Mikael, the vampire hunter who hunted vampires. While allying to find Mikael, Abby and Bonnie grow closer, which was not Bonnie's original intention. While growing closer with each other, Bonnie started growing closer to Jamie, their adopted member of the family. Bonnie has a small fling with Jamie before Abby takes off once again after being forced to turn into a vampire. However, they reconcile eventually. They currently are in contact and are closer than ever to each other.
Abby loves her daughter, Bonnie but they were estranged for over sixteen years. Abby's best friend, Miranda Sommers-Gilbert, asked Abby for help to stop an Original vampire, Mikael from killing her daughter, Elena, the last Petrovadoppelgänger. To help her, Abby lured Mikael out of town and used a dark magic-fueled desiccation spell to immobilize him but the spell drained her of nearly all of her magic. Afterward, Abby realized how much she needed to start over somewhere else, and ultimately left Bonnie to be raised by her father, Rudy Hopkins and grandmother, Sheila Bennett.
Sixteen years later, when Bonnie was trying to figure out how to opened the locked coffin Stefan stole from Klaus, she started having dreams about her mother and decided to go find her. Bonnie then sought help from Elena and Damon Salvatore in locating her.
Throughout The Vampire Diaries series
In The Ties That Bind, Bonnie, with the help of Elena and Damon, managed to find and track her mother down, and the two girls traveled to Abby's house in Charlotte, North Carolina. Bonnie then met her mother for the first time since she was a baby, where Abby revealed her past, including how she desiccated Mikael, who had come to kill Elena in order to prevent his step-son Klaus from using her to break his curse and create more hybrids like himself. However, unknown to Bonnie, Abby had already been visited by one of Klaus' hybrids, who threatened to kill Abby's adoptive son Jamie on Klaus' behalf if she didn't convince Bonnie to hand over the coffins Stefan stole from him. Fortunately for Bonnie and her friends, Abby gave her the opportunity to warn Damon in Mystic Falls, and he was able to hide the locked coffin before Klaus arrived to the witch burial ground to take the coffins that contained his siblings.
In Bringing Out The Dead, Bonnie and Abby worked tirelessly to try to unlock the magically locked coffin of Klaus', believing that a weapon to fight him was inside. Bonnie was initially frustrated by Abby's lack of magical strength, but Abby admitted that her powers didn't go away all at once—they faded away over time, making Abby believe that it was possibly the Spirits' way of punishing her for leaving her daughter. After a lot of trying, Abby and Bonnie successfully complete an unbinding spell that involved a blood knot, or two generations of a bloodline; in this case, a mother and a daughter. The power of the spell caused them both to faint just as the coffin opened, revealing Esther Mikaelson, the Original Witch and mother of the Original vampires, inside. Unbeknownst to them, however, the particular spell that they cast to open the coffin allowed Esther to channel the entirety of the Bennett bloodline, living and dead, through the two of them.
In All My Children, Esther asked Bonnie and Abby for their help in finally killing her Original vampire children, once and for all, by lending her their power in order to turn Finn (who was linked to Elijah, Klaus, Kol, and Rebekah) back into a human and kill him, thus killing the rest of his siblings. However, when the Originals learned about this plan, they forced the Salvatore brothers to help them stop it by threatening Elena's life. Knowing that Esther was getting her power from her connection to Abby and Bonnie, and knowing that the only way to cut her off from said power was to break the bloodline, Damon force-fed Abby his blood and snapped her neck, killing her and turning her into a vampire, despite Bonnie's protests. This outcome saddened Bonnie. Abby abandoned Bonnie again, despite Bonnie expressing her desire for her to stay and make things work.
In Break On Through, Bonnie and Caroline went to Abby's house in North Carolina in order to help her adjust to being a vampire following her successful transition, during which time Bonnie made her mother a daylight ring. The loss of her connection to magic was already a devastating blow to Abby's life, but when she accidentally attacked Jamie after being unable to resist her newborn vampire bloodlust, Abby became too overwhelmed with all of the new changes in her life. Caroline caught her packing up her bags, and though she assured Abby that she could teach her how to control her new hunger for blood, she could not teach her how to be a good parent, and insisted that she stay and try to work things out with Jamie and Bonnie. Bonnie herself arrived just as she was about to leave, and despite her pleas for her mother to stay, Abby was resolute in her decision and left town.
After professor Shane taught Bonnie to harness the powers of Expression, her magic grew stronger and became harder to control. Unable to help his daughter, Rudy turned to Abby for help, who subdued her daughter with magic-muting herbs to keep her unconscious while calling some witches with whom she was acquainted to come and help cleanse her from "the poison that professor's been teaching her." Bonnie, however, refused her mother's help, declaring that she doesn't belong to the Spirits anymore, but to herself only, before she left.
Bonnie and Abby seemingly made amends at some point, as Bonnie was seen sending Abby a video message stating how much she misses her and that she wants Abby to come and visit her at college following Bonnie's resurrection as the Anchor. It was revealed that Abby does not know about Bonnie's death, nor her new status as the Anchor to the Other Side, but Bonnie assured her friends that she would tell Abby everything when she comes to visit.
When Bonnie gave Damon the copy of the cure she found in the 1994 Prison World, she insisted that he give it to Elena because her mother was doing surprisingly well as a vampire, suggesting that they began contacting each other again after Bonnie's return to the living world.
In What Are You?, Abby arrives to Bonnie as she witnesses her prepare a bed for Enzo. Abby even attempts to comfort Bonnie while her daughter grieves over the death of Enzo St. John, Bonnie's deceased boyfriend. However, Enzo's funeral preparations take a dark turn when Abby sees what Bonnie is truly feeling: the dark desire to pull Enzo's soul back from hell. Abby argues with Bonnie that the darkness was leading her down a dark path, but Bonnie refuses to listen at first due to her strong motivation to possibly save Enzo. When Bonnie collapses due to the darkness clouding her, Abby burns Enzo's deceased body to sever the dark connection from Bonnie. Bonnie is finally brought back to her senses and breaks down in tears as her mother holds her grieving daughter in her arms. Later, they stand outside the house Enzo was burning in, away from the fires that were burning Enzo's body.
The Vampire Diaries (Season Three)
Bonnie: I just can't believe I'm actually going to see her. Or, well, meet her... sort of. Since I don't really remember her.
Bonnie: So, you had a daughter and a best friend and you still left?
Abby: My best friend is why I left. Fifteen years ago a vampire came to town. Looking for you, Elena. Looking for the doppelgänger. No one could manage to kill him. So I lured him out of town and cast a spell to desiccate him in a crypt in Charlotte.
Bonnie: This was a mistake. She has no magic. She can't help us.
(Bonnie is starting to leave, but Abby runs after her)
Abby: Bonnie, wait! Please don't go. Talk to me, please?
Abby: You've grown into such a beautiful young woman, Bonnie.
Bonnie: Please, just stop with the muffins and the compliments. I just want to know the truth. Why didn't you come home?
Abby: I had no magic, I was in a new city, and I realized I had a chance to be someone else - to be Abby Wilson the woman, not Abby Bennett the witch. I'm not proud of what I did Bonnie. I ran. I know I ran. But you had your dad, and your Grams... and okay, let's face it, your Grams is way better at this stuff than I am.
Bonnie: Jamie's safe. He's a little bruised, but he's safe.
Bonnie: You kept your end of the bargain, Klaus usually keeps his. You were willing to do all of this for [Jamie] him and he's not even your family.
Abby: He is my family, Bonnie. I know that might be hard for you to hear, but he is. That doesn't mean I don't care about you. I wanna help you.
Bonnie: You can't. You have no magic and I don't trust you.
Abby: When I put Mikael down my magic didn't just leave me, it drifted away. The longer I stayed away from you the weaker it got. I think Nature was punishing me for abandoning you. Maybe you can help me get my magic back.
Bonnie: I thought you said you didn't want it anymore.
Abby: I don't, but if it's what you wanted I'd do that for you.
Bonnie: You're not trying. We've been at this for over an hour!
Abby: The Spirits are angry with me for leaving you. Maybe they didn't want me to have my powers again.
Bonnie: I had all those dreams for a reason. The Spirits wanted me to find you because you're my mom. It's not them, it's you. You won't open yourself up to it. Do you know dad never talked about you? Neither did Grams. I had no memories of you. So you know that I used to pretend that you were dead? It was easier to do that than to wonder why you never came back for me.
Abby: There is no way I can tell you how sorry I am for what I did.