[Edited by Latiosmaster47, 4/5/2011 9:00:05 AM]
I recall something about that. Overloaded her body and the water in her own lung tissue drowned her. Or something.
The gallon of milk challenge is just a way to make people puke. Most people can't fit a gallon of liquid in their stomachs without triggering regurgitation, and don't have the willpower to find out.