"She's mentally damaged." If it's a result of a psychological trauma, you would say she suffers from PTSD. (That's the commonly used acronym for post-traumatic stress disorder). You could also simply say she has psychological problems. If it's the result of a physical trauma you could say she has suffered brain damage. Perhaps a more sensitive way of saying it is that "she has mental health problems because of the trauma". Never say she is mad or nuts as has been suggested here unless you are intending to be very rude. That statement would be taken as an insult.

'Mentally ill' would be the one I'd most likely use.

I believe, any of these will work well (with the appropriate grammar): - go mad - go insane - go nuts And "She has a mental disorder".