Kim,

I see myself in what you just described. It's sad, unfortunately unless she, herself, decides she's had enough, there's not much you can do.

She has very low self-esteem and feels that she's nothing without a man in her life. (I learned this from years of therapy). It's sad but SOOO true. Until she realizes that she's a wonderful person who deserves so much better, all the coaxing and begging from you isn't going to do much good. All it will to is alienate you from her and ruin what relationship you have left.

Just let her no that no matter what happens, you'll always be there for her, as a confidante who will listen. Hopefully time will help her wise up.