|Gallery of Abby images (6)|
Her first appearance occurs in Ten Sessions, where she starts eying Ted in the waiting room. In almost ten sessions, she develops a huge crush on Ted, forcing her to change her appearance to make her more noticeable to him. She tries to drop hints to him about her infatuation by admiring his least-appealing characteristics - she calls him a knight when he offers her coffee during his sixth session and makes Stella try to convince him to go out with her during the seventh session. She reads a book Ted tries to use to hit on Stella in the eighth session, and even compares him to a young Tom Selleck when he is tricked by Barney into growing a mustache for the ninth session.
After the two-minute date Ted and Stella have, Abby finds him with a bunch of flowers, and confesses that several girls have tried to convince her to forget about him, but she forgives him instantly and runs after him. Barney meets her at the reception shortly after this, where he talks sense into her and invites her to a hotel room, where she asks to have sex with him.
Sleeping with Barney hurt Abby a lot, and she tries to pay him back by putting girls on the alert, which can be seen in The Bracket (although she is never shown on camera). She alerts Lily after seeing her hang out with Barney and mistaking her for one of his conquests-to-be. Abby does this in the brief moment Barney leaves these girls alone. Because of this, all the girls Barney tries to seduce initially hit it off well with him, but after Abby's mysterious appearance, end up hitting him in the face and leaving. Frustrated with this, Barney tries to track her down (he refers to Abby as the "mystery girl" since he can't recall who she is) but fails to find her, although he does know that she is blonde.
Her second appearance takes place in Everything Must Go. When another girl Barney is trying to seduce at MacLaren's hits him in the face and leaves. This sparks the "mystery girl" in his mind and he looks around for a blonde girl, whom he sees leaving the bar. He follows her to a cab and finds out it's Abby.
When he pleads to her to stop messing around, she explains how their one-night-stand has hurt her. At this point in time, Ted and Barney are no longer friends, something which she says in words but denies in fact (because she is still attracted to him). The two end up sleeping together again, and they concoct a plan to try and hurt Ted. They play a bit at MacLaren's where they are a couple in love. Barney proposes to her in front of Ted, but her naiveté is such that she takes it to be a genuine proposal and starts planning her wedding with Barney. An exasperated Barney deceives her that Ted is still in love with her and pleaded to him not to marry Abby, and leaves, giving her a (possibly fake) copy of Ted's home address on the way out. Abby takes a look at the address and falls in love with Ted again.