Absolutely nothing in Nakomi's conversation with Aviendha points toward a Forsaken or the goals of the Shadow. The "woman" clearly knew current Aiel culture really, really well. It's somewhat doubtful she is a real Aiel, so some kind of paranormal manifestation is more likely. This is not TAR anyway, Aviendha wasn't asleep and this definitely didn't take place in one of her dreams. She might have fallen asleep without realizing it... but there's absolutely no way I can see she could wake up without realising she had been asleep, and drew the obvious conclusion she had dreamed Nakomi. Of course, there's her food and equipment as well... Aviendha would have fast figured out what she thought happened didn't really happened, if those were untouched. If Aviendha was so absent-minded that she can't tell if she slept or not, she wouldn't survive long in an environment like the Waste...

So the obvious conclusion is that Aviendha was awake and conscious, and if there's something paranormal about the visit of Nakomi, and all signs like her disappearance point to something like this, then Aviendha got a visit from a non human entity (eg: the Creator, whom the Shienarans call The Mother, which happens to be who Nakomis is in native americ. legends), or more likely, she's experienced a folding, a twisting of reality, a vision that merged with her reality - which points to an intervention by the Wheel of Time.

Nakomi merely pointed out Aviendha's reflections on the important unresolved matter of the real nature of the change to the Aiel the arrival of Rand and the LB is bringing. She planted seeds of doubt in Aviendha that the Aiel would one day return to the Waste and warrior business as usual. Nakomi just nudged, much like the Creator just nudged Rand in EOTW: "you have a choice to make" - the choice he made in TGS that Creation was worth saving, which instantly turned him into a whole new sort of Champion of the Light. To Aviendha, that the Aiel would remain Warriors was a no brainer before. Not anymore, and after her vision she knows it would spell the Aiel's doom. What Aviendha still doesn't understand is that there is no ancient "sin" to atone for, and it's not by being warriors behind the car'a'carn they will "redeem" themselves. The Aiel were guided to abandon the Way of the Leaf as a matter of survival, because for the Wheel's sake, the Way of the Leaf had to survive only as a remnant among the Tinkers for three thousand years. It's rather obvious this was so the Aiel could be there again as "Da'shain Aiel" when it counts. All it needs now is Aviendha's revelation and the intervention of LTT with facts from the AOL and the reunion of Tinkers and Aiel at his instigation. Not returning to the Way of the Leaf when they can and ought to now would be the "Aiel Sin".

The WO have been "going with the flow", with a wait and see strategy. They still have no clear idea how a remnant of a remnant will survive, nor how the others will be destroyed. Aviendha has seen a version of the future in which the remnant of a remnant is weirdly a lot more than "a remnant of a remnant" but they also don't survive Rand very long, a few generations only before Aiel as a cultural group are gone for good, and all because of their own choices. It's the Aiel, not Rand, who decided to declare some sort of vendetta on the Seanchan, and throw the world into a devasting war.

Nothing in there is the "Shadow's business". What would Lanfear or even Moridin or the DO care about the choices of the Aiel after the LB?

If Cyndane goes against Rand's lovers, and she still well might before the end, it's going to be a lot more straightforward than this.