If her stomach pain is not getting better, it might be wise to go to a pediatric Gastroenterologist.
Just a little story. When my daughter was about that age, she complained of stomach cramping and pain for quite some time. I took her to the doctors and had her tested for everything except having a colonoscopy. I eventually found out that she was being bullied by another girl in her class. Once we put a stop to the bullying, her stomach pains lessened. Is it possible that your daughter has a bully? My daughter is now 14 and even now when she has something upsetting her, her stomach will start hurting.