Secret Court by Angelina J Steffort

She set out to save her friends. What she got was a king.
Not one moment of rest for Gandrett. Not as she sets out to rescue the Fae male who was taken from her just as she admitted her own feelings for him. Now, it is up to her—to her fighter's mind, her determination, and to her growing magic that is expanding far beyond what she thought herself capable of.
If she can hold on just a little longer, she could save them all—Addie, who is suffering in the Dragon King's claws, Mckenzie, who is fighting her own battles in the southernmost territory, the young Lords of Ackwood and Eedwood who are on their own, and her brother. Her brother, who might not need saving after all as he is on his way to Ulfray. But with a king on the Fae throne who is wrongfully inhabiting it, Drew might be just as safe there as anywhere else in Neredyn—which is nowhere. Because the lands are falling into darkness, and Gandrett must save her own heart before she can save anyone else.