If you enter Nadox through the castle in Gunthak hang a left in the first room and go to the top of the ramp in the hallway you will see. She is one of the two guards standing in front of a room.
Not hard to get to but a very annoying fight. She will gate back to her spawn point up to three times in a fight and heals 30% of her HP every time she does. Beware of adds if you haven't cleared the way for her.
Easy kill for my 61 shaman but just plain annoying.