Why won't she leave me alone? (sorry...it's long)?

I know this is probably not what you want to hear, but this is probably the best option for you. Answer her calls and talk out the problems that you two are having. Tell her she is treating you wrong. And you have been helping her when she needed you, but she doesn't ever return the favor. I don't think you should add in that she is hanging with the wrong crowd, that might make her angry. But you know her better than I do. At least mention that she is not treating you right and you know that you don't deserve it. Hope I helped. :)