Imaginary Girls by Nova Ren Suma

Chloe’s older sister, Ruby, is the girl everyone looks to and longs for, who can’t be captured or caged. When a night with Ruby’s friends goes horribly wrong and Chloe discovers the dead body of her classmate London Hayes left floating in the reservoir, Chloe is sent away from town and away from Ruby.

But Ruby will do anything to get her sister back, and when Chloe returns to town two years later, deadly surprises await. As Chloe flirts with the truth that Ruby has hidden deeply away, the fragile line between life and death is redrawn by the complex bonds of sisterhood.