Eternal Embers (Dragon's Heat #2.5)

As one of the few female sentries to the Dragonstar king, Caitlyn Jacoby constantly struggles to prove herself - especially after her best friend and roommate turned traitor, resulting in the deaths of countless clan members. So when she perceives on the fringes of Dragonstar territory a potential threat from the Wyvermoons, an enemy clan, Caitlyn jumps at the chance to investigate. Instead of danger, Caitlyn finds Jackson Utah.

Cursed with immortality by a Native American tribe over a century ago, Jackson has been searching relentlessly for a cure ever since. But as he meets and falls for Caitlyn, a dragon with centuries ahead of her, he wonders if eternal life is truly a blessing.