Having gone through many years raising five teenage daughters, each one of
them has come to me somewhere between the age of 10-12 with different
degrees of hysteria because they have found a "lump in their breasts".  We
have made many trips to our neighbor's home who happens to be an Internist
who has simply said, "oh, that's just a breast bud and it's perfectly normal",
and within a year, breasts have appeared.
Each time, it calmed things down to have another person give her the good
news that it was normal, instead of it coming from Mom.  Good luck.
The fun is just beginning!
Tammy Arbeter