hi,
I was searching for my own problems and found this conversation.
I had exactly same problems since I was 14-15 years old, now I am 28. I faced same what your daughter has. I did not do anything specific. But it contnued till age of 25. Later I found I am deficient of Vitamin B12, Vitamin D3, Calcium and Iron, though I eat all types of food daily without any complaint. I did take treatment to overcome the deficiencies. After then my overall health has improved including deficiencies. I had taken supplements of Serotonin medicine through Naturopathy. Now god's grace, problems are reduced. Wish you good luck. Please write back if you have more info or need more info.
Welcome to the gastroenterology community! She might have migraines and abdominal migraines. I would recommend finding a gastroenterologist that is willing to work with you to find the right combination of medications. Good luck.
It sounds like abdominal migraine and/or CVS (Cyclic Vomiting Syndrome). See a GI and a neurologist.