She's trying to help Iris. "You have to have a good silhouette. A large bottom needs long legs. You can away with it if you have a high waist and a good carriage."
Maybe this sounds a bit personal, Sonali thinks. But you have to be objective about such things.
Suddenly, Iris is talking about their teacher Miss Boniface, who Sonali is sure fancies them both, and that makes Sonali sad, angry.
"But she has the reverse problem, tiny legs," Sonali says. It's her problem, too. She thinks her own legs are small, bandy, nearly misshapen.
Iris wipes her nose in that prissy way. Iris! Notice me, not your bloody teacher!
"Also, the legs are thick, just here in front." Sonali says, continuing, sensing that something has veered out of control. She hates Miss Boniface.
It's not like that when the music plays, and they strip down to work and they are like horses, running. Running together.