It sounds to me like simple heat
exhaustion, which temporary
memory loss can be a part of that. The way to prevent it from happening again is to ask your daughter to drink extra water, like every time she is in the bathroom, to drink a glass of water. Also, she should be put on a quality multivitamin and mineral supplement, which if a person gets dehydrated, they'll also tend to lose their electrolyte balance. And no more hot showers!