One Dark Window

Nothing comes free.

Elspeth Spindle lives in the mist filled kingdom of Blunder, where all magic comes with a price.  One evening she encounters a highwayman on her way home and joins the quest to cure the kingdom of the dark magic infecting.  To do this, they must locate 3 magic items known as Providence Cards.  But Elspeth has a secret.  She shares her mind with a mysterious entity she calls the Nightmare, and he’s getting stronger.  She’s in a race against time to find a cure.
One Dark Window has a good deal of romance, plus an interesting magic system.  It’s the first book in a duology.