Hi Myfivegirls,
I'm sorry you are going through this. I'm an adoptee myself, and hanging around other adoptive families as a kid, I witnessed a lot of stories where adoptive parents struggled with their adoptive children. No matter how much love parents show, early childhood wounds are very serious. How are your other four girls, are they adopted as well?
Living on a small town can be both good and bad. I spent my teen years in a small, rural community. While it's good that she was diagnosed, in order to provide a baseline, it sounds like she is in denial of the Dx, and is "running."
What kind of contact do you have with her? We have communication tools here which can help to reduce conflict, and may help your relationship. This can help to start:
https://bpdfamily.com/parenting/02.htmTurkish