Some others:
1) If her best friends are sluts, she's going to cheat on you, it's only a matter of time.
2) If you've been together a while, and the relationship seems like its dying and she's losing interest, and then all of a sudden she's "falling in love with you all over again," she cheated on you. She fucked another guy and then realized she made a mistake and wants to treat you right because she knows she has something special.