My 5 year old has vomited 4 times in the past hour and a half and she's complaining of a tummy ache. ?

Likely viral or food: This is likely the first stage of a viral illness or food reaction that may eventually include fever & diarrhea. I would let her stomach settle by feeding her ice chips slowly until she can hold 1-2 oz quantities of clear fluids. Chilled applesauce, popsicles, etc. can also help. If she can keep up with her fluids well enough to pee at least every 8 hrs she will likely stabilize. More than 12hr-ER