The symptoms are right in line with pregnancy. I had all of these symptoms when I was 16-and pregnant. Just a possibility to think about. I hope I'm wrong. :-) Best to you all...
I had similar issues when I was in high school and it was related to anxiety because I was under a lot of stress with all the activities I had to keep up with! I never wanted to go to school because I was afraid I would get sick at school or didn't feel well. I'm not saying your daughter has anxeity, but I would certinally be stressed if I were not feeling well and it was affecting my extracirricular activities. Something else you may try is keeping a food diary and see if there are things that she eats that bothers her consistently. Have the doctor check for bacterial or parasitic infections if this does not go away or really worsens. Fainting may have to do with malnutrition...not that you aren't feeding your daughter enough, but she may have something going on in her tummy or intestines that is causing her not to absorb all the nutreints she needs making her weak. Try giving her Pedialite or Ensure to boost her vitamin and nutrient intake. Gastric stuff is so tricky...there are so many problems to rule out. I hope you find an answer soon!