I would still question whether her skull is really a fluid filled cavity as that doctor said.
Cranford reported areas with fluid, not the whole skull. Brain parts die, then fill with cerebrospinal fluid.
The doctors seem to disagree as to whether Terri has a small bit of cortex left or none, and whether that little bit of cortex could aid in rehab.
No harm in trying, except if "the prisoner within" wants to die. But Terri's resistance to infections argues for life, not against.
Yes --- that is also a factor --- a will to live. Someone who loses that can't be kept alive, she's had plenty of chances to die I think. I've talked with nurses who worked in an ICN and they say some bigger babies with less problems will die and you have these little 1 1/2 pounders fight one obstacle after another ---- and they can only attribute it to a will to live.