What can I do to help my stressed friend out?

Well recently my friends going through a lot of stress, and I think I know the problem (even if she wont admit it) her ex-bf or should I say her on/off again bf. He treats her horribly (he's cussed her out in front of people, won't return her phone calls or texts and he always claims he's at church when really he's hanging out with his boys) (You can't be at church 24/7) and I have no idea what she sees in him. But, yet somehow she cannot break away from this dude. she knows that I don't approve of him at all. I have told her many times she would be better off without him. It seems despite how many times I tell her this (she just won't listen or maybe she doesn't want to listen) Idk She tells me time and time again I'm done with him, I'm done with him. But she never is, she's had some horrible relationships in the past so I'm sure that's a reason she's not breaking away from this guy. I've tried to do everything I can to help her out. she still talks to this guy everyday (she's probably talked to him today) It honestly and I haven't told her this yet but it honestly sickens me that she puts herself through this misery just to get heartbroken all over again. Yeah he breaks her heart every other week. What should I do or what can I say to help her realize once and for all this guy is nothing but trouble?