Mesaana is Danelle. For beginning evidence, I'll bring up the old points already mentioned. First, the entire Tower coup was boosted by the fact that Danelle had let so many extra masons in to help with the library addition. Second, all the references to her being "too dreamy" for a Brown. It could be that she just is "too dreamy," but the AS pretty much stick to their stereotypes, as well as the fact that Mesaana is described as mistakenly dreamy in the Illustrated Guide. Also, in TSR, when the AS break into Siuan's office to demote her (pg. 764), Danelle is there not looking dreamy at all (hence, mistakenly dreamy). Furthermore, at a different time, Alviarin is described as just brushing past Danelle and not even paying attention to her existence. Now, Mr. Jordan, master of irony that he is, most likely placed this passage into the book not for detail, but to show that Alviarin (who cowered and "yes ma'amed" when she knew who Mesaana was) could be made to look so disdainfully upon her master.