Thank you for posting your question. Allergy to any food item would not manifest as vomiting alone but with rash/itching/swelling/breathing difficulty or diarrhea. In the absence of any of these symptoms it is unlikely that your child is allergic to fish, in which case it clearly means that the reason your child vomits out fish is that the taste does not suit her. Absence of vomiting to other food items reinforces this theory. In such a case I would suggest that you either change the method of preperation of fish in such a way that the basic taste gets camouflaged or accept the fact that your daughter is not a fan of fish and omit it from her diet. You may later try reintroducing it slowly and look for response as taste preferences are known to change over time.