Jen, I don't think that you are being silly. Your instructor is way out of line if she is making jokes about your bra size. That's extremely hurtful and it's not necessary. I think that you would be within your rights to complain to the owner of the studio. If you live with your parents you should talk to them first about the situation.
Can you switch to another school or studio, or at least to another class? The one you're in seems to leave a lot to be desired.[/i]