Thank you for the query.
IBS can be diagnosed only if all other know diseases has been ruled out. TO do that, gastroscopy, colonoscopy
, abdominal CT, liver tests, pancreas tests, stool tests, allergy tests
should be done.
If your granddaughter havent had all mentioned tests (i`m pretty sure, she havent), IBS can not be her diagnose.
Nausea while eating, trapped gas in the abdomen sound like upper gastric problem. It can be peptic ulcer
or small intestine
partial obstruction. But without physical examination and mentioned tests it is hard to tell.
Your granddaughter should visit gastroenterologist and consider mentioned before tests.