I did a little digging and found a few references to this characters name.
http://us.battle.net/blizzcon/en/forum/topic/17346427508
If you control + F then type Synrae here you find a character with similar looks to this npc (hair colour ect) http://us.battle.net/wow/en/character/dunemaul/Synrae/simple
This character is also a shadow priest, which explains shadow form.
So it would seem this character is a reference to a cosplayer, along with the other vast amounts of cosplayers placed in-game (see the horde base in spires of arak, two cosplayers are in a building there).
Lots of cosplayers being given honorary NPC's lately.. wonder why.
Edit: just after hitting enter I stumbled on this thread http://us.battle.net/blizzcon/en/forum/topic/18300110798
It would seem she was given an honorary NPC due to the fact she arranged a nice group photo for all the cosplayers.
Still a mystery as to why the character is so rude though..
Elite
Mistress Synrae
Mistress Synrae is an Elite Humanoid, level 40, friendly to players.
Details
Mistress Synrae at a Glance
Level and Map Tracking
The game data tunes Mistress Synrae for level 40, Warlords of Draenor content.
In the Client Files
Also Friendly Humanoid at level 40 in the current client data
The highest voted Wowhead comments for this page. They are community notes, not TheWoWDB comments.
Randomly found this chick while feathering to Terrorfist. Doesn't really do anything but act pissed at you. She's just a random female NPC in Shadowform who says something along the lines of "How dare you speak to me!" if you try talking to her.
There are three possible dialogs.
"How dare you speak to me!"
"I can only laugh that you mortals keep holding on. The master even foresaw the coming of these days."
"Pathetic. Begone from my sight... I can't stand grovelers."
Community notes from Wowhead · 4 comments
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