The Midnight Star (Young Elites, Bk. 3)

Adelina Amouteru is done suffering. She’s turned her back on those who have betrayed her and achieved the ultimate revenge: victory. Her reign as the White Wolf has been a triumphant one, but with each conquest her cruelty only grows. The darkness within her has begun to spiral out of control, threatening to destroy all she's gained. When a new danger appears, Adelina’s forced to revisit old wounds, putting not only herself at risk, but every Elite. In order to preserve her empire, Adelina and her Roses must join the Daggers on a perilous quest - though this uneasy alliance may prove to be the real danger.