Chapter 24, what concept of beauty was shown by the magazine model from the days of the Rusties?

The model exhibited the concept of being thin.... overly thin.

Back in the days before the operation, Tally remembered, a lot of people, especially young girls, became so ashamed at being fat that they stopped eating. They’d lose weight too quickly, and some would get stuck and would keep losing weight until they wound up like this “model.” Some even died, they said at school.