"Sure, all things known to human experience are possible, but there is absolutely no evidence that she changed her mind before the cardiac arrest. Moreover, this was not a woman who simply lost the power of speech and kept other cognitive abilities by which she might have changed her mind after the cardiac arrest. Her brain was destroyed, so she could no longer think and she was incapable of changing her mind (once the cardiac arrest occurred). Very sad situation. But to protect the sanctity of her earlier wishes, we have to have system that makes a good determination of her last known wishes."
One question. What if the court made the wrong determination and she always wanted to live?
Sounds like an opponent of capital punishment. You can't use capital punishment, goes the argument of the objector, unless you can prove that the system can never make a mistake.
The answer for enforcing people's right to die is the same as that for capital punishment. Our system is careful enough that mistakes will very rarely occur and the good coming of enforcing the rights of so many to rightfully die with dignity outweighs the occasional (hypothetical) 'mistake'.
By the way, the system is more likely to make a mistake in forcing someone to wrongfully live who clearly wishes to die than in allowing someone who wishes to be maintained to die. Poor Terri is an example. In our effort to be "sure" she was forced to be debased and diapered for 7 years. That was a great wrong to her.