Mesaana meets with Alviarin. She tells Alviarin to learn why the heads of the Ajahs are secretly meeting together. She believes that Galina is dead. Alviarin notes that she is actually wearing a dress of bronze silk with black scrollwork. (TPoD,Ch25)
(Wot encyclopedia)

If Mesaana were Tsutama, it would be simple for her to learn why the Ajah Heads are meeting herself, instead of ordering Alviarin to do it. Mesaana obviously thinks that the Highest of the Red ajah (Tsutama, of course) participates in these meetings, since she's annoyed that Galina got herself killed.

Also, I like Tsutama and hope we get to see her again, it would be a shame if she was Mesaana.