Main character was in a relationship (high school, I think) with this girl that seemed to be cheating. Rather than confront her partner, she breaks contact, or something to that effect. Later (after college, I think), she finds this person again (who, for some reason, does not recognise the main character), seduces her, enters in a relationship with her, and then quits her job, moves, and breaks all contact, as revenge for the cheating years ago. The cheater manages to track her down quickly, though, and convinces her to give her another chance. "Is it not more amazing I fell in love with you twice, not knowing you were the same person?", or something like that. It is still subtly implied at the end that the cheater is, well, a cheater...