Can Food Allergy Cause Constant Nausea?

my daughter has suffered for the past 6 years with constant nausea. she has lost weight, is unable to hold a job and cannot live normally for 24 years old. we have seen several GI doctors, have had all the tests, and even had gall bladder removed, all for naught. She can only eat a small amount and gets full, then nauseau starts; whether she has eaten or not. She is desperate; the next thing we are doing is seeing a food allergist. All tests have been negative except for "old inflammation of stomach". When she eats, she needs a bathroom almost immediately. She's afraid to go far from home for this reason, plus constantly feeling ill. Not very much pain associated with this. Can a food allergy cause this?