K.D.
Sounds like food allergies or sensitivities, especially if she spikes a really high fever that goes away once the stomach has emptied. I'd keep a diary of what was eaten when it happens and see if you can figure out what it is. For our oldest son, the way a food was prepared made a difference. Tomato paste or any canned tomatoes would give him problems while fresh, even cooked, were fine. Just a few thoughts. Since it's just occasional, it's probably something you can handle on your own by just avoiding the offending food. GL!