I believe your friends attorney should be able to request all of the childs' medical information including mental health. The judge would make a decision on the request and if the mother does not comply with said request, would be held in contempt of court. I don't think she would want to go there.

Your friends' attorney should also ask that the child be seen by another doctor/therapist to be tested and that report can be entered into court as well.

Another option would be to have your friend make an anonymous call to DCYF (or whatever it's called in your state) if they feel there is some kind of abuse or neglect going on. If they get involved, then they too will be called into court to make a report of their findings. This though, can be a slippery slope so one should consider it very carefully.