How to get over my girlfriends tough past?

[bill]

Hi I'm 17 and my girlfriend of 2 months is 16, I love her a lot but she has had a really bad past. I am like a completely straight edge and don't drink or any of that stuff at all. Now she suffers from depression so that is much to blame for all of this but, starting at about age 15 for her she was getting drunk with her friends, taking prescription pills, and also cutting herself. She also was dating this bastard 19 year old guy because he was the only one that would pay attention to her at the time and he abused her. A few times she would run away from home and go with this guy for hundreds of miles to places like New York City for days and get drunk and stuff there. Now she got arrested this time a year ago with that guy for alcohol possession, and he got pegged with DUI, and statutory rape (although that never happened, she is still a virgin). That guy is now gone and she hasn't heard from him since. In the following months she got more depressed because of that and her parents finally found out about all that stuff and she got in serious trouble. She was still drinking and cutting until she went to a church get away in July. It was there she said that she found god and decided to turn her life around and has not gotten drunk since July. And it has gotten better since then although it was very slow. She then dated this 17 year old black guy that also abused her and she still fell victim to and was still cutting. Now she has improved and she hasn't cut since early November and I took an interest in her in late November. I knew her for the past year but stayed far away because I knew she was into some bad stuff. It was November I learned that she wanted to get better and wasn't really like that anymore and for more reasons my heart just went out for her. Although she still liked me way before I finally decided that I could like her. So December 3rd I asked her out and she said yes. I guess I cared for her and I wanted to be there for her and keep her safe with all the crap she has gone through in life. Now ever since then she has improved so much but it has taken a lot out of me. I almost feel like a hypocrite for being involved with someone that was doing bad stuff that I devoted my life to staying away from. And every single day I have had a picture in my head seeing her drinking, or cutting, or with some other guy and I feel so heart broken every single day when I think about it. She still does talk a little about her old life and I hate it when she does. Whenever we have a discussion about it, it turns into a big fight and we both get upset. I know that what's in the past is done but it is so hard to get over all of that stuff. I don't want to think about it anymore but it just comes into my head and I don't want it. I want nothing to come between us. Don't get me wrong after all this negativity, I love her a lot but sometimes she just makes it so hard. I want to get over all these heart broken feelings but something is keeping me from doing that. Please help me and tell me something we can work on. Also thank you for reading this whole long thing.