Russian Stories, book 1: Rusalka
Carolyn J. Cherryh1989

She is the tormented ghost of a murdered girl, pitiless spirit of the wilderness, who prevails only upon living souls. And her name is the most dreaded in Russian folklore. Rusalka.

Impetuous Pyetr Kochevikov, a fugitive from Voyvoda with a price on his head, has none of the superstitions of his fearful young companion, Sasha, as they flee through the vastness of the forest.

But when they arrive exhausted at the cottage of the wizzard Uulamets, Pyetr is dismayed to learn that he can mock the spirits no longer. And when he finds himself enchanted by Uulamets' beautiful and wraithlike daughter, no mortal power can assuage the Rusalka's terrible thirst for life...