SG22, I'm wondering if you have already looked at McLean Hospital in Massachusetts -- it sounds like you have explored so many options that it wouldn't surprise me. If not, you can check out their web site for child/adolescent MH treatment here:
https://www.mcleanhospital.org/child-teenthey post their phone number on that page.
Their adolescent DBT program is called 3East (
https://www.mcleanhospital.org/treatment/3east) and a brief description reads:
"Our programs focus on treatment for depression, anxiety, post-traumatic stress disorder (PTSD), and emerging borderline personality disorder (BPD). Symptoms of these conditions include suicidal thoughts and behavior, self-injury (such as cutting), disordered eating, drug and alcohol misuse, impulsivity, and significant interpersonal difficulties."
You could also try calling their phone # and seeing if they could refer you to somewhere else -- perhaps somewhere they know about that would be a better fit that you and I just haven't heard of.
I'm so sorry you and your family are going through this excruciating experience. I hope you find a program that gives all of you some peace.