don't think this will be much of a problem, since nobody is even nude....

CUBS(children...)
have boxy shapes, hips are not defined, breasts are not defined.

ADULTS...
more of an hourglass shape, hips and breasts are clearly defined.

EVEN in small-chested females, adults do have their breasts slightly defined, although they are not as large looking as a bustier female...

this is by no means professional, just basic guidelines as to how to tell a cub(in this case, cubs under 12-13ish) from an adult female.
please, if you disagree, don't start shit in the comments.
I'm just trying to help a little bit....