>>26
You have two solutions:
-be there when she has a fight with her boyfriend, and plant seeds of discord. Shoot him down, show her his weaknesses and insecurity (of course, don't be too obvious, duh)

-NEVER BE THERE AGAIN while she's with the guy. Make her understand that you're okay being friends but you don't want to be the one picking her pieces back everytime some other asshole breaks her. Seriously dude, it's your sanity at stake here.