I logged back into a horde alt where this quest giver was gone earlier, after doing the dailies on an alliance toon, and the quest giver was there once more. Not sure what exactly causes it but I'd say there is no reason to give up, just wait around or log between your characters now and then to see if it is there. Either a layer thing or a random despawn/respawn thing, by the looks, but certainly possible to get a hold of the quest even if buggy.
Edit:
I have four horde alts left that did not do the dailies due to the bug. I decided to camp it on one of them. After 15 min she spawned. I grabbed the quest, speedran the targets and returned and she had already despawned, so now I am writing this as I wait for the respawn to turn it in. So gotta be quick and keep an eye out if you can be bothered to camp for this one before they fix the bug.
Edit 2:
Managed to turn it in on the aforementioned toon the second time she spawned, then she despawned almost immediately again.
The next time after that she stayed up for several minutes and I was barely able to run through the other 3 in quick succession before she despawned again, so you just gotta be patient and/or lucky if you want to do this before the bug is resolved.