At first I thought that Laras, the Cook was Mesaana. Then while writing my thoughts on Who killed Asmodean?, I realized that there are two Forsaken in the White Tower and that Laras is most likely Semirhage!
Known facts about Semirhage
An unusually tall, dark eyed woman, with remarkable charm and grace (The World of RJ's tWoT p.65)
She likes to do needlework (p. 65 LoC) and has been seen making the same pattern of tiny flowers that Laras teaches to Min.
She is an ally of Mesaana and Demandred
Demandred and Mesaana know where she is located
Assumptions
Her disguise would be easier if she can't channel because if she was in the tower and did
not mask her ability to channel. Unless the Forsaken know how to make it look like they are less strong in the Power, she would attract too much attention because she is Much
more powerful than any Aes Sedai in the White Tower and they would sense this.
She would probably want to assume a position where she had a free run of the tower
Given all of the above Semirhage must be Laras the cook. We have not met many woman at all
in the tower who can't channel and Laras is the only one that has been described in any
detail. That is not enough evidence on its own, but we have many more clues:
Laras helped Siuan Sanche escape. Why would a cook take such a risk for somebody she knew
as little as she knew Siuan Sanche. But as a Forsaken, she must have known that a siuan Sanche
wandering around alive and well could cause much more trouble for the Aes Sedai
than a dead Siuan Sanche. One of the Dark One's best weapons is always dividing its enemy
and making them fight amongst themselves.
Laras also went to Sheriam to request a lighter punishment for Nyn, ELayne and Egwene (p.338 tDR). Why would a cook do this? Does she want to free up the big 3 Accepted so the Black Ajah can capture them?
Siuan thinks that Laras looks fatter than she ever did. Why would this be so? Did Semirhage kill Laras and then assume her identity?
Min thinks that it is strange that a woman like Laras would know so much about Lively Women. And Laras takes great pride in teaching Min things like Needlework and how to attract men. Semirhage has been known to pass her time knitting during meetings of the Foresaken.
There are also numerous occassions when we have tongue in cheek comments about cooks and women who can channel... (to be continued).
As a cook Laras would seem to have a free run of the tower because she plays a big
role in the discipline of novices. What better excuse to wander around the Tower than to tell
a sister how one of her Novices is performing her tasks.
Where is Semirhage?