Just to wrap it up, this worked for all my friends too! 
Thank you Callysto \o/
At least we have a workaround now until Blizz fixes it.
This worked for me too. Thank you!
Ive been teying to get this to work for a while now. Had to abandon the quest 4 times. But i finally got it work by reloading by UI… gettingnaked, letting her hit me a couple times… kited her back about halfway, the DISRUPTED her (which as a 70 killed her lol). Only then was i actually able to speak to her and complete the quest as normal.
When i tried to jsut kite her back so it would trigger the trap she faded once i got close to her sister.