I don’t care how little the girl is, if she has a health issue she has to be made to understand what she can and cannot have, or don’t send her to people’s houses. How old does she need to be to understand that she can get very sick from eating certain foods?
Also, maybe she has a mild allergy. Some people get a reaction just from being in the presence of peanuts. BH she is fine, but don’t blame other people for their negligence.