Unrecorded verbal contracts are considered a bad idea for a reason. They devolve into he said/she said. I agree that the court was left with a nasty choice, but IMO they made the wrong one. Morally, they needed to start with the base presumption that she wanted to live, and require documented proof that this was not the case.
There's at least some movement within the biomedical ethics community to declare people like her as "dead." Obviously the law hasn't caught up. For the record, I don't agree with this, but there's definitely been some discussion on it in peer-reviewed journals.
An incapacitated person must have someone else make decisions for them. Keeping someone "alive" for decades because it's technically possible makes no sense. In our society, the person who gets to make that decision is your next of kin, which for her, meant her husband.
I'm sure we all know how difficult it'd be to make such a decision.
For the record, if I'm ever in that position, please pull the plug as soon as possible. I don't ever want to "live" like that.