What Causes Fainting, Nausea, Dry Heaves And Chills?

My daughter is 19. She has fainted a handful of times in her life. She is 5 1 and weighs under 100 pounds. She is currently several thousand miles away from home at college. Yesterday, she felt nauseous in the middle of class; she dry heaved, had a bowel movement and fainted for a second. She had chills and was sweating and got a headache. Her symptoms subsided and she felt extreme fatigue. This morning, she chose to stay in bed, continues to feel nauseous, is short of breath and very tired. She has a GI condition called SIBO that causes her to also be gassy and bloated and have stomach cramps when she eats high in sugar and simple carbs. She is currently on ADHD meds, as well as a host of supplements and vitamins, but nothing new. Her iron was tested this summer and was normal. Any ideas what could be wrong?