She's already dead
The worst case scenario is there's some tiny part of her still alive in her brain stem, silently screaming: "Please let me die! Please let me die!" However even that is unlikely. Her parents have been extremely irresponsible through this ordeal. Their only excuse and it's a slender one, is their ethics was clouded by their religion (it can happen to otherwise decent people).
Lesson to be learned: If you have a loved one who has just suffered a major brain injury then get it over with quickly while it only involves you and the physicians. Don't allow idiot relatives with lawyers to get involved and make a mess out of it.
Gary