Flawless Girls by Anna-Marie McLemore
The Soler sisters are supposed to be polished and poised in polite society, but they aren’t. Their grandmother, who has raised them, has not cared until now. She realizes that life will be especially difficult for two Latina girls if they can’t at least blend in with their manners and attitudes. Grandma is able to get both girls a spot at Alarie House, a prestigious and hard-to-get-into finishing school.
In one day, younger sister Isla has come back home. She cannot do it, and she cannot stand how fake everything is at Alarie. Older sister Renata, though, sticks it out and when she comes home months later, she is a completely different person. Isla sees Renata behaving with eerie politeness and pleasantness…and murderousness. The night Renata returns home, she also vanishes.
While Grandma does what she can to find Renata, Isla decides to go back to Alarie House and find out what’s going on there. But it is a demanding finishing school and it certainly isn’t going to simply tell Isla what’s going on.