Reddit reviews Food Allergies and Food Intolerance: The Complete Guide to Their Identification and Treatment

People can have food hypersensitivities that don't show up on skin or blood tests for IgE-mediated allergies.

However, blood testing for IgG antibodies to the foods isn't diagnostic for such things. Maybe having high IgG antibodies to a food is a good thing - after all, allergy shots increase one's IgG antibodies to the allergens, and that reduces the allergic reaction.

The "gold standard" right now is doing a careful hypoallergenic elimination diet followed by food challenges to test each food that was eliminated, and see if something bad happens. There aren't any commercially available, reliable blood tests.

Hypoallergenic elimination diets can be super-strict (more reliable but difficult to do) or less strict. Brostoff and Gamlin's Food Allergies and Food Intolerance has a good section at the back with elimination diets of varying strictness.

If she doesn't otherwise have allergy problems - such as allergic rhinitis, allergic asthma, etc. - this kind of food hypersensitivity is a lot less likely.

Or, if she otherwise has autoimmune problems, that makes celiac disease or some kind of autoimmune gluten sensitivity more likely.

So maybe she'd hear advice about a more reliable way to diagnose food hypersensitivities.

I don't think food hypersensitivities would have anything to do with an ovarian cyst, though.