Can my girlfriend of 3 years file for abandonment?

Well my gfs mom dropped her off at my house when she was 13 years old with 1small box of clothes and all of her other things in this small box. That's all she had. At first she even had her own room and my room wasn't even on the same story of my house. Now we are both 17. Her dad lives in Oklahoma and he was abusive got put in prison for beating her mom to death almost and beating his kids. He started doing drugs right when he got out and now after running from cops trying to go to Canada and everything he got caught and was put in AA and DA got off of dope,cocaine,crack, and whatever else I don't even know and now he tells her mom who don't care about her kids (let's her son smoke cigarettes he doesn't even go to school and he is 14) that he wants her to move to OK with him and stay till she's 18 she doesn't want to and we just found out she is preggo was not conceived at my house but his in ok cuz she was only supposed to stay for the school year only but now her mom changes her story and bows down to her dad and says she's going back! Can we stop this anyway at all? My mom has made her doc appts got her clothes food a stable place to live and much more. My mom now considers her as a kid not my gf even. My mom is just as heart broke as me in this situation. Her dad says she's never coming back I'm not going to see my kid I'm paying child support and much more. I no he can't make me pay it's just what he thinks because I want to be a part of my kids life and she wouldn't file. I can go on much more about the horrible things I just will leave it at that. So what can we do? She's in ks with me right now only for a little bit for summer break.