Do you run into burning buildings?
Would you jump off the lifeboat and swim back into the titanic.
Would you buy a cute tiger kitten thinking it would love you forever?
Not to be rude but these are RED FLAGS. Do yourself a favor and RUN.
Does it matter to you if she and her current boyfriend make it? What are you getting out of this "friendship"? What part of what you wrote above attracts you to this situation? Do you believe you can "rescue her"?
Use your mental energy elsewhere.