The Orphan Queen, book 2: The Mirror King
Jodi Meadows2016

Wilhelmina has a hundred enemies.
Princess Wilhelmina is ready for her crown, but declaring herself queen means war. Her magic is uncontrollable, and now there's a living boy made of wraith - destructive and deadly, and willing to do anything for her.
Caught between what she wants and what is right, Wilhelmine realizes that the throne might not even matter. Everyone thought the wraith was years off, but already it's destroying Indigo Kingdom villages, Princess Wilhelmina's ability might be just the thing to help reclaim her kingdom - or ruin it forever.