Rusalka

A russian version of those water sprites of irish legend, who look like beautiful maidens and turn out to be nasty spirit stealing monsters. CJ Cherryh's Rusalka turns out to be a witch and lives under an extremely unfriendly old willow by the riverside.
This can't be the same willow obviously but it's definately got a presence. And is that a twiggy, brushy, sleeping maiden lying down behind him?