This is a key question. If she hasn't had a comprehensive evaluation (6-10 hours of appointments across multiple days), it would be a good thing to do.
From what you describe, she is not likely to have full-blown Reactive Attachment Disorder (RAD). She may or may not have attachment issues. Some kids are not neurotypical, and do not "attach" the same way. There is no question she has issues and challenges.
It's tough to get all the details into a first post, so hope you don't mind more questions. Sounds like you have at least 2 kids - maybe more? And that the autistic brother is older than this girl? How old are the kids?
I'm just another parent with challenging kids... so this is just something to think about. Consider what you describe of her behavior. Difficulties transitioning between two homes. Very needy, very demanding. She could very well have developmental challenges and/or mental illness.
