Hi~ It sounds like you have a sick child on your hands!
Nausea,vomitting,diarrhea,abdominal pain,and fever a can be serious in a 10 year old.
I see you live in the UK. I'd bring her to the hospital to be evaluated. Dehydration is a big concern here.
Good luck!
I'm so sorry to hear that your little girl is so sick. There aren't any doctors on this forum, but with her symptoms I think you should consult a pediatric gastroenterologist. They can be hard to find depending on where you live. You might call your insurance company for guidance in finding a ped GI doc on your plan. Just out of curiosity, has your daughter ever had any abdominal surgery or trauma? Any other health problems? I hate the though of such a young girl being so terribly ill!