Welcome to the board. Leave the report as it is. She won't be the only child with ADD diagnoses in Davidson. It will not hurt her application. All you need are the scores.
The head of the lower school sounds like a perfect candidate. Let's face it most of the people don't even know what Davidson is. Having recommendation from the violin teacher is a good idea too.
At the end of the day it's the numbers that matter. The fact that she is accelerated at school and the head think she is a good candidate is a great bonus.
Good luck
