When the hematocrit and hemoglobin are high, it's called polycythemia, although most of what comes up if you google that is about polycythemia vera.
I had elevated hemoglobin (mine was 16.9) and hematocrit (50.1%), a few years ago and it was a side effect of a medication I was taking; after I was taken off of it, it took about six months for them to really normalize and they are still towards the upper end of the normal range.
Your daughter's levels are not dangerously high, just abnormal. They would be normal if she was a man.
Some causes of polycythemia include:
Polycythemia Vera, a condition that is not commonly found in children and which causes the body to produce too many red blood cells.
I read one paper some time back on hemoglobin and hematocrit levels in adults with type 1 diabetes and they were higher than in type 2s and in controls, at least in that one study. It was of just the patients in one clinic and the authors decided to study it because they had a patient with type 1 diabetes who had an extremely high hemoglobin level.
I can't locate it right now because pubmed is giving me error pages.
P.S. Being at high altitudes and having difficulty breathing will also cause the body to make more red blood cells.
dx age 17, now 25
on Lantus for 7 years; on minimed 530 G since 12/7/13