a. As soon as Min started talking about the "three" prophecy in The Gathering Storm with Callandor, I've assumed that it would be Nynaeve, Moiraine, and Rand. Even if callandor isn't what the prophecy is about, I think the three of them will link to use it. In ToM he tells Nynaeve that he needs another person he can trust "Maybe Elayne or Aviendha." The second Moiraine shows up he'll know who the third is.

b. Nynaeve and Moiraine are the closest connection that Egwene and Rand have to each other, but I think Egwene trusts Moiraine's opinions a lot more than she trusts Nynaeve's. I think she could be important in helping them come to some kind of compromise at the Field of Merrilor.

c. Whatever she gained from the 'Finn, and I have no idea on that.