Finish rinnys quest line then it will open
rinny is in the forest iirc you gotta help free her from fairies
Edit: wait I'm dumb LMAO you probs mean where she is in Transylvania, she's at the succubus tower, it took me awhile to figure out how to get there too, I think it's the left when you first enter Transylvania? There's a fake wall you can go through