Most people do not think of life in such clinical terms. Very few of us know what such an incapacitated state would be like. Who would take the chance of having someone dehydrate us to death knowing there was a remote chance that we would feel the experience. Would you recommend that you go to the dentist for a root canal without anesthetic? Would you recommend dehydration if you knew in the process you would experience worse pain than a simple root canal for days; pain so bad that it would cause you go into involuntary convulsions?
I have a test for you: go get a hammer, put you thumb down on a concrete floor and whack that thumb with the hammer as hard as you can. I hope you would have the I.Q. to realize that it would be a stupid test and be smart enough not do do it. I believe that Terri Schiavo was smart enough to keep from whacking her thumb with a hammer.
I am not under any illusion that all, or even most, people would share my views on all this, much less that Terri Schiavo would in particular. The whole point that I began with is that I don't pretend to know with any confidence what she wanted.
But, I do know what I know now, and what I know now is that that's what I would want if I were in a vegetative state as it's understood to be. Yes, I would rather just go by lethal injection, but if the options were either death by dehydration or irreversible vegetation I would choose the former.