Goddess of the Rose — P.C. Cast

It's not a green thumb that's kept the Empousai family's roses blooming for centuries--it's the drops of blood that their women secretly sacrifice for their gardens. But Mikki, the youngest, would rather forget this family quirk and lead a normal life. Until the day she unwittingly performs a sacred ritual and ends up in the strange--but strangely familiar--Realm of the Rose. As its goddess Hecate reveals to her, Mikki has the blood of a high priestess running through her veins. And the Realm has been waiting for her...

In a flash of temper long ago, Hecate cursed her guardian beast, along with the rest of the Realm, with a permanent slumber that only a high priestess can undo. Now nothing's coming up roses--and Hecate is counting on Mikki to set things aright. Awoken, the beast at first terrifies Mikki--but soon compels her more than any ordinary man ever has. But the only way he, and the Realm, can be saved is for Mikki to sacrifice her life-giving blood--and herself...