It's a bad idea man. She's completely out of control, and you're starting off with her in control. She doesn't want to go to rehab? Too bad. Amy Winehouse's dad said she didn't need to go to rehab, and look what happened. The conditions for living at your house are: she has to attend rehab first, she has to go to school, you'll be drug testing her twice a week and if she fails she's back in foster care, she needs to dress appropriately, and she follows curfew. If you don't think you can hold to that then she's going to walk all over you, and your house will be just another failed placement. I'm in social services, so I know how manipulative drug addicts are, and it's honestly going to take a ton of time and effort to get her back on track. She's also probably experienced multiple traumas from the things that she's done to get drugs, and she may start acting in a sexually inappropriate way towards you. She might have some PTSD if some of the sex wasn't consenting. She might end up pregnant and still using drugs (you said she had a serious boyfriend). Your younger kids are going to see all of her bad behavior. You need to talk to a therapist about this first, and talk to her case manager. Ask them what you can realistically expect. Maybe watch some episodes of Intervention and pay attention to how the drug addict manipulates their family by using guilt and anger. It's not going to be like raising a normal child or even a normal teenager. I've seen kids like that break their families, and it doesn't improve their own lives either. Sorry to be a downer, I'm just trying to help you understand what you're taking on. If you really understand then you have a better shot. That's why case workers are so straight up when they tell you about the problems that a kid is having.