http://familydoctor.org/familydoctor/en/teens/puberty-sex...
There is a wide range, of when girls start puberty. Some say they start between 8-13 years old. Some resources say it is between 9-14 years old.
So, a girl does not start puberty EXACTLY at 11 years old.
Some girls even start developing breasts by 9 years old.
My daughter is 11. She BARELY has any signs of breasts popping up. Many of her classmates, are that way. Then there are other girls who have HUGE breasts already. Such a wide range.
Some girls even get their periods at 9 years old. Some at 12. Some get hairy legs before they even get breasts. It really can vary.
I really do NOT understand why... your daughter's Pediatrician is concerned she has not developed breasts yet or that she has not shown puberty symptoms yet.