Welcome. Many of the kids that bring us here are adopted, my own included. While many have traumatic pasts, it seems that adoption itself proves traumatic. I read recently that half the young people (I don't remember the age; sorry) in therapy were adopted!
You will find support here and good counsel. But it seems like we have a smorgasbord of ideas, that are kind of one size fits all, for new members. When we know more about your daughter and the circumstances, we can begin to be more specific with ideas. I have found that the thing that benefits me most from this forum is writing out what I think, and feel, and what I know. And it's as helpful or more helpful to post on other peoples' threads. After all, most of us are in the same boat.
I agree with everything Busy said. Has she had a neuropsychological exam? Best to go to a regional children's hospital. They could help you refine a diagnosis. You can get a referral from your pediatrician. Does she have an IEP? Services through special education could help. Is she vulnerable? Is she easily influenced? What does she say happened? Has she spoken to you about what happened? What is her attitude?
I think it's time to lock up your money and valuables. I also think she needs to experience an increase in structure and supervision at home as well as school.
I agree with busy about expressive arts therapy and I agree about equine therapy, which can be free, if she has an interest in horses.
If all of this happened at school, is school aware? I think there needs to be an intervention so that your daughter is not around this other child. I think she needs more supervision at school. An IEP could help. The neuropsychological exam could help you get special education services.
I might think about calling the police to talk to her; not that she be punished but that she understand that there are consequences to breaking the law, and she has broken the law; even by stealing from her mother. They will talk to her with kindness and care.
Are you involved with a spiritual practice? This is my biggest regret with my own son, that I did not involve him in my faith. I think children need moral/spiritual/involvement, teaching and community.
What is your daughter's peer group like? How can you support her to get into a good group of kids, with common interests? Did I ask about hobbies? What about socially?
Is she close to family members? Who?
Does she talk about her past?
I hope you keep posting. It helps. Take care.
PS While I don't believe she should be punished, I do believe she needs to experience her life changing as a consequence of what she did. This cannot be same old, same old. She needs to know that stealing is very, very wrong. And that life will not be the same for her, with this kind of behavior. Is she showing regret and remorse?
I am thinking about this other child who sold her mother's phone. For what? Drugs? I would be very alert to the possibility of drug use. Why is she hanging around this child?