A.R.
N.,
from experience I myself developed quickly and my right boob was developing bigger then the left. It wasn't noticeable to much to me at first, then my mother took me to the doctor. She had explained to me that this was normal and happens to girls who develop fast. Not to worry. several month later you wouldn't even had known I had that problem. You have done the right thing in letting her know she is fine, she will be . From experience .
A.