The problem with a lot of liberal analyses of the sexualisation and objectification of women in the media is that they fail to identify the political reason behind it - namely, that relegating women (and, increasingly, girls) to sex-class status supports male power in society. If our most important function is to be looked at and consumed as objects then we can never take our place in society as full human beings.
Therefore I disagree that the pressure comes solely from the beauty industry/media. The beauty industry exists in order to capitalise off the construction of women and girls as sex objects - it does not create this structure.
This might all sound a bit heavy to lay on a teenager, but I find the constant invocations on self-esteem boosting sites to 'just ignore the pressure - you're beautiful as you are!', really fail to get to the root of the problem and are therefore ultimately not much help to girls who are trying to navigate this hyper-pornified culture. THEY know that, whatever mantras one might repeat about looks not being the most important thing, that if you are female in this society then looks are indeed the most important thing about you.
Twisty Faster at I Blame the Patriarchy has a series of hilarious and razor-sharp articles pointing out the anti-female grotesquery of impossible Western beauty ideals:
blog.iblamethepatriarchy.com/category/the-beauty-ultimatum/
Here she is on the debacle of 300,000 women with leaking breast implants in Europe and South America:
300,000 women aren’t dumb. But instead of getting an invitation to life’s rich pageant, since the cradle they have done nothing but absorb messages that illuminate their many defects. As a matter of survival they have been forced to embrace femininity as their prime directive. Land a dude and beget the son and heir, etc.
Now adults, these women perceive that, as members of the sex class, their prospects with dudes — and in fact their value as human beings — depend entirely on the degree to which they succeed in appeasing the dominant class. They grasp that greater rewards accrue to women who display sexual availability than do to women who make no effort to submissively self-pornulate. They further observe that they belong to a culture wherein large breasts are fetishized. They surmise that they will achieve higher status, and in turn be happy and loved, if they conform as closely as possible to the fetishized ideal.