L.B.
I have a 6 yr old daughter that my in-laws are trying to tell me that she is developing. I think that a lot of girls now are developing sooner than they would due to growth horomones in the beef and milk that we eat and drink. I remember developing much sooner than most girls in my class. Plus it also depends on genes, if you developed early she may very well. You may also look at mom and g-ma in law and ask a few questions about thier development. If you think she is really developing then I would start with those little tank tops they sell to go under regular shirts. And the just roll with the development punches.