Sounds similar to my friend's niece. She was only diagnosed with aspergers when she was a young adult.
I am really not familiar with the American system. Here, it is not the psychiatrist that usually makes these diagnoses but a psychologist. Is it possible to have her assessed again?
I get the whole tough love and letting them find their own way... But I'm not sure how I feel when there is a possibility of a mental illness (as you have mentioned). If that were the case, she may lack the foresight to understand her situation and make any sort of changes. Although she lives with XW full time, doesn't necessarily mean that the decision is up to XW.
I'm not sure if I'm remembering correctly but, didn't D want to stay in the house with you at one point?
Me:38.. H:33. Two beautiful kids S:6 D:3 M:8.. together for 11. Bomb dropped:10/17/11 Separated:11/07/11