Always get documentation. Yes, when she is 16 and sometimes younger they can choose who they want to live with but no she can't just come and pick her up any time she wants. If she wants custody or your 16 year old wants to live with her mother. It all needs to be done in the courts. I think you have handled it well so far but you do need to get everything in writing. Write dates that things happened written down so if you are questioned as to why your daughter can't sleep over night at "moms" that you have something to fight with. Get a lawyers advice they can better tell you what you can or cannot do. Some lawyers won't charge for advice. It gets really tricky at your daughters age. I would also get any documentation from the police about when she was picked up. If there is going to be a fight in the courts you need paper work. Something in writing, a journal, police records (on your daughter and/or mom), school records (like what happened to her grades and it written that this happened after she went to live with her mom), keep it all together. It had helped us out a lot.