I just did this quest last night, if memory serves, once you get to the maze it's right until phase (teleport), left until phase, forward until phase, then behind you. Hope that helps.
Where is this wyvern? I have look for 2 hours upstairs and seen every one except her, used see invis just incase and wondered the maze past wurms which was quite frustrating since no matter where you got you end up getting to a teleporter on floor the ports you somewhere else, I give up for today... Any help would be greatly appreciated. Can't find a loc online anywhere for her....