Well, to check for development, i could understand feeling the not so visible labia. But then she exposed you to check visually anyway. Maybe there's a reservation about looking & feeling at the same time. But if you're feeling & not looking, you may wind up feeling "around", which you wouldn't have to do if you could see what you need to check.
Now, unless your clothing caused your breast development to appear ambiguous, i question the necessity to reach up,& cup them to check for development. Unless she wanted to be quick & spare the time & embarrassment of undressing/redressing.
Which raises a question similar to airport security situations. Would you rather be patted down/ felt up, or viewed nude after a strip search / body scanner ? I donlt think the answers would be unanimous. I think they would be based on a combo lesser of 2 evils embarrassment/awkwardness/feeling of violation, and for some, the bigger thrill of being seen vs touched.
Now, say i'm a female medical professional at a school. Do i want a girl to run home and say "Mommy, she reached under my clothes and cupped my breasts !" or "Mommy, she made me undress to check my development !"
Me, i think I'd be more comfortable with the latter scenario as sounding more like acceptable behavior. But that's me.