Relationship help. My girlfriend?

OK, me and my girlfriend have been going out for around a year. She turned 17 just on dec 24, I will be 18 in march. She has a baby with another guy. I love the kid, thats not the issue. She grew up in a very conflict prone house. Most of her family has been druggies. There has been some ual abuse. Her father was physically very abusive and the whole family has had no luck at all with men. They see us all the same. Her mother loves me, but doesn't want her with me because I am not a christian. Her sisters generally don't like me because they are druggies or mean to her and I don't put up with it. I have been nothing but supportive with her, very patient and helpful. I even suggested therapy which she attended and I drove her too. She had to stop after a few sessions because of lack of money. No one wants her with me. Her family all thinks she should just be with the father of the child. But the thing is, he is very abusive, a high school drop out, a druggie and has d her. We do not get along! But the thing is she has cheated on me a lot with him. She has recently stopped. I know, I'm stupid for staying, but I do love her. Yes we are very young, I know. So if this is all your going to say don't bother. Every time we start to do good she gets scared and does something to ruin it. All she knows is the chaos of her old life and doesn't know what to do when she is happy! I can read her very well and we just had a long talk today. She agrees she thrives on conflict and doesn't know what to do when shes really happy. She's scared to love again, be whole with me, and be happy. My question is how do you help someone like this be happy without the conflict? I've tried. People say just not to be with her and she's needs time alone to think. But without us together she can't stop herself at all from going back to her ex. He's very manipulative, and was with her for three years so he is in her head! I know she loves me otherwise she just wouldn't be with me! She cries when we talk. Sh knows what she's doing is killing me and us! But she just can't seem to stop. I want to do whatever it takes to help her. I'm no psychiatrist but I know her and read her well. She wants to change but we need help on how. So please give me idea's! I need them. I'm all out. I'm the opposite of her ex. I am in school taking many honors courses, don't touch drugs, I even got her to stop! I love her daughter like my own, she was only a few months when we got together. He's only seen her maybe 10 times in around a year. He uses her to control my g/f. He cares nothing about the child. He has never even kept her over night. I buy her things, babysit, teach her, I was even the first person she walked too! Her family also always tells her just to be with him because she needs her father. But I would rather have a great step father than an *** hole real father who is abusive! So thanks for the help. Again the question is how to help her since all she knows is conflict so when it's not there she creates it because she thrives on it!