There's sensation and there's emotion. They're not the same.
My point is that we cannot know what Terri's body is feeling in the former sense; she may be in great pain.
It is my firm belief that in cases like this the patients' lives are artificially prolonged for the sole benefit of the relatives. That's wrong, in my view.
And sooner or later, that tube will be withdrawn and Terri will be allowed to die.
The compassionate thing to do would be to do that now and let her parents get on with grieving their daughter.