Don't get me started on the whole under/over arm thing. Oops, too late 
Throwing overran results in a faster ball. But throwing underarm is slightly more accurate. Throwing underarm actually strains more muscles and is more likely to lead to damage.
Even in professional sport women are expected to throw under arm. This makes them less good at throwing and carries more risk of pulled muscles. Then they get told they're not as good at it.
Why are women expected to throw underarm and men throw over arm? Just because women should be more dainty/feminine.
Thank goodness that women no longer have to wear tight restrictive clothing during sport which prevents them playing well. Oh, no, there was the Australian women's basketball clothing for the las couple of Olympics, and all that fuss over beach volleyball. Hmmm, perhaps women really are being prevented from competing as equals.
Btw, I would hope that if my dd spoke to me about something like this, I would deal with it appropriately, and it wouldn't shame her into silence. I wonder why exotic is trying to dissuade the op with such an emotional argument? If my dd had talked this through with me, it could well be that she wanted me on her side and helping her to voice her thoughts about it.