Probably Verin.

But it does remind me of an interesting theory I read a while back. You remember back when the SG were escaping from Ebou Dar, and Aviendha made a weird gateway that for some reason required a lot more strength than gateways normally do? When you look at the times given in the descriptions around that scene, it appears that Avi MIGHT have created a gateway that allowed her to go back in time a couple of hours in addition to moving from place to place. Its nothing conclusive, but there are enough weird things surrounding the event that it is suggestive if you read it closely. Anyway, what if the woman was Aviendha herself from the future, guiding the younger Avi to try and avoid the mistakes made by the aiel in the future(as we later see through the columns).

Just my looney theory of the day. It was probably Verin.