First of all, I had a b/f who was the same was as her current b/f. You really do feel trapped b/c the one you, at least like, is saying they will hurt themselves. I soon realized that if he does, he does and that's his own fault, not mine.
2nd, unfortunately, I would say to break it off completely. You two may have a good thing going, but if she completely breaks up with her b/c and then starts dating you, I think you'll have trouble from the exb/f. If anything, I would give them a few months to sort things out and then start dating her officially. You don't want the exb/f still in the picture!
*~* ShEllyLAy *~*