SandraHi Susan,
Here is my theory, I think it might just be her anxiety that is causing her stomach to feel bad. She might get herself so worked up about going to school that it causes her to have stomach aches. If you have everything else checked out and nothing is wrong...
Does she have problems at school with work or other kids? Does she play any sports or involved in anything? I’m not sure how to handle anxiety in kids. I would hate to drug them for it. Maybe you can try to talk to her to find out what is causing her the anxiety and work with that. Maybe you can expose her to more of the situations that make her anxious, work through those so that she gets to a point where they don’t make her anxious anymore. Just throwing out ideas.
Good luck,
Sandra