I broke up with a girlfriend once because I felt the exact same way. I'm not saying she will do this to you, but I felt like I wasn't being fair to her as she just wanted to be close to me and be around me and I was so worn out and tired that I would push her away and be distant/quiet. I didn't want to be around her when I was like that. I lived in my head and being the introvert I am, it takes energy for me to be around people, energy that I didn't have. I broke up with her because I thought she needed to be with someone else that would feed her need to be close because I just couldn't do it...and it wasn't fair to her. It really was a "me" problem, whether she chose to believe that or not. Someone told me that you have to love yourself before you can love anyone else...I think that's true. I wasn't (still not) at a point of loving myself and I knew it. There is some major healing to be done, perhaps she has some to do too. Is she in therapy at all? I know that's helped me.
I hope this post doesn't scare you, there is no guarantee of what's to come, but if you give her space and as much time as she needs, things could turn out alright. Just depends on if you want to wait.
Edit: I guess I should clarify, I have been on both sides of the fence with addiction. I am addict, but my father was also an addict.