YA Fantasy about Ghost friend (M) who our MC befriends (F). One character is called Kai.

[Deadline]

About ghost friend (M) who our MC befriends (F), one of the characters is called Kai. The book cover looks relatively Blue, with a jack frost looking boy with white hair somewhere on it.

My memory is a little fuzzy, so some details may be wrong.

[bookel]

Year read was ....?
Were the characters 9-12 or teenage?

[Becca]

The Valley of the Wolves by Laura Gallego García?

[Kris]

Becca's suggestion of The Valley of the Wolves by Laura Gallego García looks promising.

One description on Amazon:
- "Odd flashes in her sapphire-colored eyes at birth are the first sign that Dana is unlike anyone else in her impoverished farming family. Her only childhood companion, Kai, lies across "a perplexing abyss"; he appears to be a boy of her age, but he is visible only to Dana. After an elderly stranger offers Dana an education at his distant academy, Dana's journey to understanding begins. The stranger is a sorcerer, and as Dana works through her apprenticeship, Kai by her side, she begins to question her benefactor's motives and to explore the terrifying power of the magic she has inherited. ..."