Faerie Blood by Anna Applegate

A missing King, a headstrong Prince, and a Queen who can’t see past her grief makes for a bad combination.

The tension between the Unseelie and Seelie has turned into a full out war, one that Cora is unprepared to handle. With less than a year of training under her belt, she’s forced into the fight while trying to keep a level head for both herself and the prince, a nearly impossible task. They’re constantly torn between their blossoming love and the war that’s growing each day.
When Noah makes the terrible decision to hunt down the King alone, Cora must see him safely to the frontlines of the Seelie army, although the journey is more dangerous than either of them bargained for. Especially when finding the King means crossing the border into the Dragon Lands as well.
Noah and Cora are stronger together, especially when they have each other’s backs in battle. But when death is on the line, and an eerie truth is revealed, will their love be strong enough to give the Unseelie a fighting chance in Faerie?