I would have thought a food intolerance or allergy, but I don't believe that is ever accompanied by a fever (I could be wrong and I'm sure someone will correct me if that is the case). It sounds like a tummy virus. Unfortunately not much can be done for that beyond waiting for it to pass. However, if it continues (especially the pain) make sure the Dr.'s are pushed to further explore.
Her Dr. is the best person to advise you, but I can tell you from personal experience with a very long tummy virus (my 2 year old had rotavirus..it lasts a very long time) the most important thing to watch for is dehydration. Water does not do the trick. It's best to give her pedialight, apple juice diluted with water, even ginger ale (complelely flat, no bubbles) diluted with water. She needs the salts and sugars to stay properly hydrated. I also found plain chicken broth worked well. Dehydration is the biggest worry with vomiting, so even if she isn't keeping it down, make sure to keep giving it to her anyway. Even milk is fine if she will tolerate it (they used to say no dairy with tummy bugs, but my pediatrician tells me that is no longer true).
When my son had rotavirus, he would vomit and have diarea for days on end. This went on (on and off ) for months. If they haven't done so, and this continues, I would request that they test her stool. My pediatrician said that is the best way to diagnose a virus. But do keep taking her in.
I hope she feels better soon.