Hi
Welcome to the MedHelp forum!
One possibility is severe acidity and gastric reflux. Your daughter can take Omeprazole empty stomach in morning and see. Monitor her diet, log in what she eats and see if there is co-relation between what she eats and her symptoms. At times adhesions formed post surgery cause sub acute intestinal obstruction and this could also be a serious cause. Electrolyte imbalance is another possibility. Take care!
It is very common for people who have had this procedure to have problems like your daughter is experiencing. Many people cannot eat high fat content, dairy products, they become lactose intolerent and some even have problems with some fiberous vegetables, I suggest that you monitor her intake and reaction to certain foods and see what does and oes not bother her. Again this is very common.