Everything has its reasons....it could be true to this woman. We may not call it "life" that she has, but being in a vegetative state, she must have been experiencing another life dimension(after all, God is still allowing her to live?!) If we look at it at face value, it seems unfair. But maybe, while she is in that state, something has been transformed, something has been polished...not just on herself, but to those who have been in contact with her...
One thing we can do is to continue loving, continue caring...that could be the last thing that they will experience. Even in that state, they can feel. We don't know what it could do to them.