Hi and welcome. I am sorry to hear about your sister.
I am not sure how much help I will be but I did find some threads that might be helpful to you. They are on our Son/Daughter board as that is where most of the discussion regarding RTCs take place.
I do know from my reading here that McLean is supposed to be an excellent facility and I believe 3east is a part of that. I am wondering if you could contact them and ask them for an interim referral?
In the meantime, here are some links that might be helpful to read:
https://bpdfamily.com/message_board/index.php?topic=114267.msg12588412#msg12588412 (scroll down a bit in this post to see the links)
In the meantime, what other recommendations were made for your sister? Is she in school and receiving services through the school system? Your parents may want to post on our
Son/Daughter board as well.
I hope this is helpful to you and your parents and I wish the very best to your whole family.