My 20 year old daughter is healthy and eats very healthy and is active. She just was working in a hot school that had fans going. She ate a good breakfast. She felt faint, says everything went black so she sat down and put her head between her knees. She then threw up. She has done this about 6 times in the last year, not all related to heat. She is healthy, so it doesn't seem like this should happen to her. No chronic diseases. Should I be concerned?