Not kill, let her go - she's already dead.
Withdrawal of support (feeding tube, respirator, stabilizing medication, etc) is the only legal option for allowing someone to die now. All but the feeding tube will typically result in death in minutes.
Starvation will take days. That sucks.
Why can't we use the same lethal injection protocol used for capitol punishment? Its specifically designed to be humane (unlike starvation) and I see no difference between this and "putting down" a terminally ill animal.
"It is forbidden to kill; therefore all murderers are punished unless they kill in large numbers and to the sound of trumpets" --Voltaire
"Whenever you find you are on the side of the majority, it is time to pause and reflect" --Mark Twain
"The significant problems we face cannot be solved at the same level of thinking we were at when we created them." --Albert Einstein
"This is still a dangerous world. It's a world of madmen and uncertainty and potential mental losses." --George W. Bush