Duel of Fire by Jordan Rivet

Dara is a competitive duelist in a fiery mountaintop kingdom. She’s on the verge of dueling glory when she’s asked to train with Prince Siv, the heir to the throne. Handsome, charming, and utterly infuriating, he refuses to take the sport—or her—seriously. When threats emerge from the shadows, with the careless prince as their target, Dara will have to raise her sword to protect him—but even her skill might not be enough to keep them both alive.