The Whisperings in the Shadows (Shadow Series Book 1) by Bekah Berge

SPFBO6

Marble Moreno isn’t exactly human. When the Collection—a group of radicals dedicated to cleansing the land of magic—shows up in her village, all those tied to the mystical receive a spot on their kill list. Upon realizing that Marble is the daughter of a Sea Prince, and that magic runs through her veins, the head of the Collection captures her. Yet, instead of taking her life, he seizes the opportunity to force her into finding a cursed chest that no human can touch. A chest hidden deep within the walls of Stonegarde, a heavily protected school dedicated to educating the realms’ aristocratic Sovereigns and their servile Lackeys. But if she fails, he’ll put a knife through her mother’s heart. Inspired by the resemblance between Marble and Princess Zamia—a Sovereign who has never found her decoy, her doppelgänger, her Lackey—the leader of the Collection weaves together a plan that places Marble in the Princess’s path, ensuring her entry into the school.