What can I do with my 12 year old daughter

Hi I'm new here and I need advice. I have a 12 year old daughter who's almost 13. She recently moved with her dad that she just met a few months back. With a broken heart I let her go live with with because she didn't want to live with me since she met him. Her dad and I spoke about the situation and the stuff he needed to do to register her in school, he seemed like a mature man with a wife and more children. She's been there over 2 months now, since she left the house she's doing everything she wants , she even was seeing smoking with some people . Her father hasn't done anything to register her in school or to get a lawyer to get custody of her, I've seen his not such a good parent . But she doesn't want to come back and live with me , she told me so many times that if I force her to live with me she will kill herself or run away or she will hit herself and call the police on me. I told her that her father is not doing anything to keep her there so that at some point she will have to come back with me , she said first she had to be death. So today I went to the police station since I have no idea what to do, they told me that I could bring her but i can also leave her there and if she doesn't get to go to school that's gonna be the father responsibility not mine. The thing is I want to bring her here but I'm also afraid she will do something to my baby son or me because she threatened me before saying she can make my life terrible. I would like her to go to a juvenile hall because if I leave her with her dad she's gonna be a bad person in the future. The police told me that juvenile hall only a judge can make the child go there and in the mean time she would have to live with me. I don't know what to do, should I let her go or bring her back? Please help I need some opinions via /r/Parenting http://ift.tt/2vcImBM