Does this girl go to the same school as your daughter? Would there be any resources at the school ... counsellors, a nurse or social worker ... that you could express your concerns to? It sounds like more going on here ... definitely an endocrine disorder, and not necessarily diabetes (her post-meal blood sugar wasn't overly high). I'm thinking adrenal dysfunction, possibly Cushing's syndrome.

Having a third-party get involved might be a good idea .. since you don't want to jeopardize her friendship with your daughter. Good luck to you

Doreen