Gimme a break, Cain ... you know EXACTLY what's going on here. You have a sad girl who's fatally attracted to a bad boyfriend and looking to you for a lifeline because she's crushing on you. You know the ending already. She'll break up with him (again!) and get with you, but she'll go back to him like a bad penny when he temporarily treats her better.
So it's all fun and games for you because you aren't emotionally attached, and you pretend that you are on the high road because you aren't encouraging her to cheat (not directly at least). Why bother? Because it will get you laid with no guilt or commitment. Do you drink milk with those ego cookies??
Sheesh.
Carl.
ps ... I'm "old school" LF too!!!