All states have adopted no fault, but the Petitioner can also plead whatever grounds they see fit. Either way, you get your divorce, it's just no fault makes it easier. Which is actually in Terri's favor!!
It's not exactly called "divorce by proxy" but an incapacitated person can indeed be divorced and no power of attorney is required.
The problem is that the divorce must be requested by the spouse. Michael Schiavo isn't doing so.