I've defeated the warlock in the manor, and now I cant seem to find her. What should I do? It says that the manor is empty.

Iif you recruited her, she should be in your camp. If the manor is empty she's with you or you kicked her out, and i think she's gone forever.

If you didn't recruit her, you made her leave the Mansion forever. Nothing can be done now, just start the new game. And next time either have Charisma 8 or sacrifice your butt to have her in your team.