the Witch is found in the dark swamp after exploring for a bit it's a random encounter. and the lizardmen story did you give her normal or strong restrain potions?
The following locations are where the 3 lizardesses can be found:
The Lake inside the Forest
The Dark Swamp
And the Ruins when you get the option to check on the 2 or so warriors that is going away from the others during the Evenings, which i think is around 18:00 or so on the game time.
