Again, what a stellar point you are making.
I see your point. Since we don't know exactly what she was trying to say, we should just assume she wants to die, and kill her.
We MUST err on the side of death in all cases. That's the moral way.
The irony here is the fact that she SPOKE when asked the question!
Whether she was going to say 'I want to live' or 'I want to die' still indicates she is NOT brain dead.