The weird guys inside the House of the Undying sais they had been expecting Dany for a long time, and also said that they sent the comet to help her find the way... that seems proof enough for me that the comet was intended for her, the mother of dragons!
That was an illusion. Those guys didn't exist, it was a trap playing on Dany's delusions of grandeur, that's why Drogon kept her from entering that room.
The actual Undying, the undead warlocks in the final room, never claimed they had anything to do with the comet.
Edited by Catastrophe, 11 January 2012 - 04:47 PM.