It definitely sounds like she has a serious cognitive problem. I would not hold it against her but I am surprised that the vet could not give anesthesia her to have x-rays or something done so you can get an idea what you are dealing with. At any rate if it is a brain tumor or something very serious you may have to have her put down. We had a bird operated on for a eye tumor and it came back as a brain tumor with a vengeance. It did give us some time to say goodbye.
Putting her down may seem cruel but after suffering a stroke and going up the long hill to recovery I know first hand how your own body can feel suddenly alien. At first I didn't think things would ever get better that I would read and write ever again. I did not realize how much resilience I possessed. Reading through blind spots for years they finally disappeared one day. It must be terrible for her to be trapped inside a sick mind please be kind to her. In her mind right now you could be some stranger attacking her. In my opinion brain injuries are the worst because when any part of your body is injured you have pain but the brain controls everything. When you lose your mental faculties you lose the essence of who you are.
It would have been good to have a diagnostic to be sure though.