That Thing about Forgiveness

Allyson discovers her lover for several years had been cheating on her with another woman. The breakup was ugly and even though her lover begs her forgiveness, Allyson's heart is hardened to the point that revenge is clouding her judgement and forgiveness is out of the question. So both former lovers isolate themselves from all social interactions except work. Allyson's friends do their best to console her, and even try to get her mind off of her former lover and get her to go out and party.
Even Allyson's sister is trying to put the pieces of the relationship back together since she is worried about both of them. In her role as mediator, her sister has to listen separately to both Allyson's and Kehli's side of the story and try to convince them to patch things up. The futility of the situation has Allyson's sister at her wits end and tries to bow out. At the same time a work friend convinces Allyson to come to a co-worker's birthday party with her.
At first she refuses fearing she'll run into Kehli there, but she is promised there is no way Kehli will be there because it's a party at the home of someone Kehli doesn't even know. 'What could go wrong?' her friend asks Allyson.