The hag DOES spawn however in the cage room when bugged. She just doesn't get out of her invisibility and makes no effort to attack you. She's on the small plank bridge above the activation sphere thing. When you place some aoe effect over it (as in not actually creating the effect, but only placing with your mouse), you can see her red circle. I used a bugged prayer of healing scroll to find her, and then fire bolted her spot to make her drop the invisibility. She doesn't fight after that though, you can just backstab her repeatedly.
