Hey Joker,
There's not a lot you can do other than to continue to be there for her and to continue to support her. She needs to come to her own conclusions about her boyfriend, only she can decide if he is right for her or not. It's never a good idea to get involved in someone else's relationship.
Hopefully she will eventually see the light if her bf really is that shoddy, and then who knows what could happen between you guys. But for now just stay out of it, and when she is berating her boyfriend to you try not to get drawn too much into that. Like I say, let her come to her own conclusions. That way she can never blame you in anyway for anything that happens with her relationship.
I hope it all works out for the best, for you and for her....