For what it's worth, you sound like a "dysfunctional rescuer".... I'm not insulting you, as this is a case of it taking one to know one 
You can't save her, protect her, keep her on the straight and narrow. Your job is to make yourself the healthiest and best-functioning you that you can.... and she is dragging you down. I understand your feelings better than you may realize, so I'm trying not to be harsh here, but you need to move on. Cut the ties, make some new friends, and start moving in a direction that's going to build you up not drag you down. I'm reminded of the words of Maya Angelou: "When someone shows you who they are, believe them.... <i>the first time</i>"
In other words, this probably isn't going to get better, and has every indication of getting worse. I think you know this. In fact, I get the impression you already know exactly what's best for you, but you're just holding out that faint hope that something will change. Been there, and I understand. Unhealthy relationships do tend to change -- they get worse. Start fresh. I sincerely wish you the very best
You can't save her, protect her, keep her on the straight and narrow. Your job is to make yourself the healthiest and best-functioning you that you can.... and she is dragging you down. I understand your feelings better than you may realize, so I'm trying not to be harsh here, but you need to move on. Cut the ties, make some new friends, and start moving in a direction that's going to build you up not drag you down. I'm reminded of the words of Maya Angelou: "When someone shows you who they are, believe them.... <i>the first time</i>"
In other words, this probably isn't going to get better, and has every indication of getting worse. I think you know this. In fact, I get the impression you already know exactly what's best for you, but you're just holding out that faint hope that something will change. Been there, and I understand. Unhealthy relationships do tend to change -- they get worse. Start fresh. I sincerely wish you the very best