The Defiant Heir (BOOK 2: Swords and Fire trilogy) by Melissa Caruso

Lady Amalia Cornaro, heir to a powerful family, and her fire-wielding partner Zaira are drawn into rising tensions between the Raverran Empire and the magical Witch Lords of Vaskandar. When mages start vanishing, they journey into enemy territory and attend a dangerous Witch Lords' gathering. Amalia must navigate politics, magic, and uneasy alliances to protect her empire.

A mix of fantasy, diplomacy, and adventure, this sequel deepens the stakes and character relationships.