Normally you should have gotten this quest some callings ago. Normally "Empty Darkness" is the next upgrade your friend after "Reflections Past", but you are are the second person I heard of which somehow has problems to get this quest (the other one being Gulian).
As far as I remember you already did the Promyvion-mission, so the problem clearly isn't the part about never being there and friendsship should be more than enough also.
I'm not sure but how about this: before you enter a Promyvion you have to 'log in' with the large apparatus in the hall of transference and then you can enter just this single promyvion. Do you automatically get 'logged out' after you killed the boss of a promyvion? If yes, perhaps you have just to log in to a promyvion again before you get the quest.
Perhaps your friends is, well, kinda afraid of going to that place without proper equipment. Has she the highest weapon tier?
The last part is just the conversation: you have to talk about 'quests' not to 'chat' to get "Empty Darkness" activated. Hm ... "Empty Darkness" isn't marked as a quest in the questlog and you get the queststarter-comment from your friend just once, so perhaps you have gotten the quest already and just missed the text at the rendezvous point. Have you tried to go to a promyvion and checked the rendezvous point there?
Tell me if you can get the quest with one of this hints, if not I'll search the web if other people have also this problem and look what I can do against it.