Suggest Treatment For Vomiting And Stomach Pain In A Child

My granddaughter is 6 years old. I kept her home Monday of this week, she complained of her stomach hurting. She has vomited Monday about 3 times and on Tuesday the same. I kept her home on Wednesday also. She went on a field trip with her class on Thursday. She has had no fever . Now today just a few minutes ago she had diarreah and vomiting, again no fever. Foul smelling stool, sour smell. Should we wait and take her to the ER. There are cases of the flu here in Ann Arbor, MI, Washtenaw County . She is up running around and says she feels fine. What to do?