TheWoWDBI'm sure it's just a vision or hologram or something. If not I'll be surprised.
After all, her model (view in 3D) is the night elf version from Well of Eternity, not the present-day naga Azshara.
Elite
Dalaran Teleport Client Actor
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Even if she isn't in this expansion, the addition of this NPC points to some kind of appearance, perhaps a flashback, perhaps a vision. Anyways she being "mentioned" points to some later appearance of her. It would make more sense (IMO) if she ends up appearing in the next expansion, so this NPC may be some kind of "breadcrumb" to the next expansion's story.
(sorry for the bad english.)
Seeing that she has golden eyes instead of silver, i'd say it is just an update to fix the lore-related mistakes Blizzard made on her model in Well of Eternity. However, it looks like that was fixed in a hotfix patch for 4.3, and this new datamined model just makes the eyes glowier.
I also think her more blueish skin-color fits with the lore that early Night Elves evolved from Trolls.
Details
This roster comes from the current game client's data files, so it is not a complete list of every NPC in the game - older world NPCs that are no longer in the modern client are absent.
Community notes from Wowhead · 11 comments
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Level and Map Tracking
The game data tunes Dalaran Teleport Client Actor for levels 10 to 45, Legion content.