A female channeler can estimate the potential of another channeler very accurately.

This is a skill that is utilised in the Tower on a continuous basis, and taught to novices at a very early stage.

The reasons behind the loss of Traveling and the exact length of time since the last dreamwalker are misinterpreted and inaccurately remembered bits of historical information. Not a current skill which is highly refined, like estimating potential is.

I know you WANT Egwene to be close to Nynaeve in strength. But that is unfortunately not what the books tell us. And it is clearly not what RJ portrayed.

To quote RJ from memory (and please correct me if I use the term Wondergirls instead of Egwene or Elayne or Aviendha or whichever of those three he used in his quote):

"The Wondergirls are a step up in strength from modern Aes Sedai (feel free to insert the name of the specific Aes Sedai he may have mentioned - it might have been Moiraine), and the female Forsaken are another step up from them."

So that gives us a clear indication that RJ saw Ewgene to be sitting roughly halfway up the ladder between modern Aes Sedai at the bottom and the average female Forsaken at the top.

If we are interpreting RJ's "steps" as referring to absolute jumps in strength, then we can show quite easily that since Egwene is roughly twice as strong as a strong modern sister, that you can add another strong sister to Egwene's full potential to get to Nynaeve's strength.

That means that Nynaeve is as strong as 3 strong sisters, and 50% stronger than Egwene.

If, however, we see RJ's "steps" as proportional steps up, then it means that if Egwene is twice as strong as a strong sister, then Nynaeve is twice again as strong as Egwene (since the proportional gap represents a doubling of strength).

I tend to be conservative and lean towards the former - the absolute jump in strength. Which is the lower estimate of the two.

Which - to conclude - means that Egwene is two thirds as strong as Nynaeve, or put differently Nynaeve is 50% stronger than Egwene.

Egwene = 2 strong sisters
Nynaeve = 3 strong sisters.

Lanfear is significanlty stronger than that, and might come close to equaling 4 strong sisters, which would make her capable of at least standing up to Rand for a short period of time. This is necessary seeing as Rand is able to face 4 sisters quite easily, and Lanfear should theoretically be able to come close to matching him.

If you understood the books as well as those of us who have been reading and debating about them for over a decade, then you would see the bigger picture here.