Matt, unfortunately we don't know the full extent of this lady's injuries; nor do we know the extent of their long-term consequences. I think you would agree that it could be the case that allowing her to die comfortably would be the positive result.
Now, I'm not suggesting that anyone pray that she die - but I seldom pray purely for a cure for someone, especially when I know as little information as I know here. Instead I pray that God will guide the doctors involved in a person's care to know the right thing to do at any given time - but where the medics have already given up any hope (and of course that happens on rather more occasions than some would like to accept) I pray that God will do what is best for the person and people involved - the patient and their family.
I think that the idea that 'No' is necessarily a bad response is faulty; how often does a parent say 'no' to a child's request because they know (or at worst, believe) that saying 'yes' will place that child in danger or at risk?