Hello! Thank you for the query. The most common reason of such nausea after eating is acid reflux disease. Such symptom can be also caused by peptic ulcer or gallstones. If she has also pain in upper middle abdomen and chest burning it can be peptic ulcer. If the pain is in the right upper abdomen and sometimes radiates to the back, gallstones are possible. IBS or/and anxiety can also give such symptoms however usually causes diarrheas or constipations as well. To make sure what is wrong she should have abdominal ultrasound, full blood work with liver tests (AST,ALT,GGTP), pancreas amylase, bilirubin level, urine analysis and pregnancy test. If no findings, upper GI endoscopy should be performed as well. Hope this will help. Regards.