The Gilded Crown by Marianne Gordon

The Witch's Heart meets The Foxglove King in this debut novel about a woman who can bring people back from the dead, and the princess—and only heir to the throne—that she must protect, no matter the cost.
The first time Hellevir visited Death, she was ten years old...
Since she was a little girl, Hellevir has been able to raise the dead. Every creature can be saved for a price, a price demanded by the shrouded figure who rules the afterlife, who takes a little more from Hellevir with each soul she resurrects.
Such a gift can rarely remain a secret. When Princess Sullivain, sole heir to the kingdom's throne, is assassinated, the Queen summons Hellevir to demand she bring her granddaughter back to life. But once is not enough; the killers might strike again. The Princess's death would cause a civil war, so the Queen commands that Hellevir remain by her side.
But Sullivain is no easy woman to be bound to, even as Hellevir begins to fall in love with her. With the threat of war looming, Hellevir must trade more and more of herself to keep the Princess alive.
But Death will always take what he is owed.