That's odd. "Shipwrecked Anubites" is the quest that gives you a choice, as you can complete it in an easy way (by finding their boats and supplies) or in a hard way (by killing Kravenrook).
If you choose the former and report that it's done, the anubites will leave the place.
If you complete the hard part, you can have sex with the priestess.
As far as I remember, it doesn't matter when you kill Kravenrook, because its head is stored in the inventory. And you can just visit the priestess and tell her you have killed the beast, then she will reward you before leaving.