The Warrior Princess of Pennyroyal Academy by M.A. Larson, 359 pages

Evie and Maggie are still enjoying the glow of their victory as they travel into the forest on their coach. But the happiest day of Evie's life is suddenly turned upside-down when they're ambushed by witches. They dash back to the Academy, only to learn that the witches have been attacking every coach that tries to leave. With their supplies nearly depleted, the Academy surrounded by witches, and new dangers looming outside the castle walls, Evie must devise a plan to save her friends and clear a path for the princesses and knights to escape.
In The Warrior Princess of Pennyroyal Academy, M. A. Larson brings Evie's exciting adventure to a close with even more magical mischief and heart."