2 gallons is a lot of water for anyone to ingest, even over a few hours.
Public outcry will likely yield a settlement, signed waiver or not.
If there is negligence, a signed waiver is worthless. You cannot protect youself from you own negligence by having somebody sign a form.
And this is waaaaaay beyond negligence. This is knowing, willful, malicious, etc. You can't waiver you way out of that.
I agree. But she made the choice to do that. There was a case a few years ago in Florida (I think; not sure) of a kid who inadvertently drowned himself (according to the autopsy report) by drinking 8 8-oz. glasses of water in about a minute after playing outside. Should the family have sued the public water utility?
Granted, prior to hearing of that kid's death, I had never heard of drowning yourself that way, but this turned out to be a tragic accident.