Personally i am torn on this, because as you say who has the right to decide if a person should live or die. But since she has been like that for 15 years and has made no improvement i think she should be allowed to die, but i don't think it should be done by removing the feeding tube and letting her starve to death-thats inhumane, it should be done with drugs so that it's quick and painless.
I think that if she is in constant pain and has no quality of life and isn't really concious (sorry i'm not sure of the right word) of her surroundings tehn it is unfai keeping her alive.