There is a whole, very large, industry which devotes itself to the activity of making women feel bad about themselves.
It is called fashion.
Girls on the verge of womanhood are particularly susceptible to its malign influences. They perceive fashion as an instrument in the process of conformity and belonging. They are - too often - not able to resit its blandishments and be themselves.
School uniforms might be seen as an antidote to its influence, but even these are adjusted, distorted as far as possible to be peceived as fashionable.
In a similar way, they perceive the activities displayed in mainstream pornography as indicating normal sexual practice. Many of these activities show aggression towards women.
So far my girls are both oblivious to fashion, to the extent that my eldest sends
me out to buy stuff for school trips etc because she knows I will come back with something vaguely cool enough. The body image thing is a whole other topic though. From year 6 they are taught in school to count calories and being fat is stigmatised. So far I think my girls have been ok and we talk about dieting, eating disorders, airbrushing in magazines and fat shaming a lot, but quite a few of their friends have 'fasting days' or just don't eat at all during the school day, even though they aren't at all overweight.
I've posted on here before about the harassment my eldest got from a classmate last year. Forcing/tricking girls into viewing porn, making rape jokes, asking girls if they'd like to be raped...how normal this is I don't know but the school has now banned the use of smartphones. Still, she regularly gets asked what her bra size is etc.
To answer Jeremy's point, yes, the figures aren't clear cut and I did arbitrarily say maybe a third of those with anxiety about sexual harassment were anxious through paranoia rather than with real cause. But something is going very wrong if young girls are feeling like this. I suspect that social media, smartphones etc are making harassment both easier and more acceptable.
As for negative comments, as you rightly point out HH this is a terribly delicate age and 'joking' comments from family or sarcasm from teachers goes deeper than it should. But again we have social media where people say things that they wouldn't dream of face to face. And teenagers can be incredibly cruel. Many of them of course will see celebrities being trashed in the media for putting on weight or having cellulite, and such unkindness becomes normalised.