Suggest Treatment For Headaches And Fainting Spells

My 19 year old sister fainted and hit her head on the floor. She said that she thinks she fainted for about 2 seconds or more. She was at the sauna for like five hours before she fainted. She has eaten dinner. She had mild headache and claims that she doesn't have any pain anymore. I have heard that a person that hit her heead shouldnt sleep for a few hours after?? And any sleeping positions recommended?