I would just keep track of everything she ingests, to rule out food allergies. So no treats unless you know what is in them, and keep a list of what she eats when, to see if there's any pattern.

As a person with food allergies, I can also tell you that after a bad reaction (vomiting and "loose stool") I do NOT want to eat, and am honestly not even feeling hungry for a couple days. Thankfully I haven't had any change in my allergies lately!