Not a medical doctor, but from what I can gather her condition is pretty rare. Usually the brain stem is damaged (which causes brain death) but in her case, it was not severely compromised as the rest of her cortex was.
The stem contains the necessary hardwiring for autonomic functions like breathing and temperature regulation, but it cannot be taught to do anything more, that I am aware of.
No, she is not brain dead. If she were, this would not the issue it is, but she has no hope of regaining anything, and will conceivably carry on like she is for some time to come.
I don't believe I have ever heard of someone in this state who has never had a bed sore, and that indicates her care is exceptionally good.
I have only come in to contact with a case like this on one other occasion. It was a stroke victim. He passed within eighteen months, and I suspect the situation was much the same without a family squabble and courts.
There have been many before her to be dehydrated while not suffering from a terminal disease.