I find this story pretty depresssing to be honest, it's not so much the fact she didn't know that drinking too much water can kill you, it's the simple fact that parents feel they have to go to these lengths to make their children happy, and that commercial enterprises will encourage and feed off of that need.
If my child was in Danger, I'd surrender my own life to save them, if my child wanted a Wii, they can damn-well get a part time job and earn the money, that's how I got my telescope years ago, and, at the risk of sounding like an old git, it was actually treated like something valuable and worthwhile because of it.