Raine: A Dark Elf Fairytale - The Darkwood Chronicles, #3

A Dark Elf princess embarks on a perilous adventure to save her world.In the shadowed land of Elfhame the Hawthorne Throne is in grave peril, and the heir, Prince Brannon Luthinor, is nowhere to be found. He and his human wife have crossed between the worlds in pursuit of the Dark Elves' ancient enemy. Only one person has the courage to follow: his sister Anneth. But the mortal world is far more complex than Anneth expected.
Desperate to find her brother and his wife, she instead stumbles into danger of her own. Her only hope of protecting those she loves is to give herself up to the enemy, and risk sacrificing everything for the sake of a mortal prince.*From USA Today bestseller Anthea Sharp, a fantasy romance filled with sweeping, epic adventure.