Agreed then.

And yet, Graendal casually threatens Demmy in WH, and doesn't mind challenging Lanfear to an OP duel.
And it was the other way around, by the way. She assumed Semirhage was the strongest of the three, and then reconsidered that it might be Demandred.
Then she coolly thinks of defeating either.
I think an ant would be squished in the actual difference in overall ability in the Power these three have.

Okay!

Thematic link need not mean arch foe. And Moggy as Nynaeve's arch foe is laughable, currently. With her strength, her angreal, her ter'angreal and the fact that she has defeated her twice before, all combine to make it inevitable that Nyn will wipe the floor with Moggy.

But the contrasts between the two were being emphasized even more! In one chapter, we have Semirhage talking about the cruelest pain she can give. In the next, Nynaeve realizes that sometimes, pain is needed, and should not be healed away.
In one chapter Cadsuane realizes that the way to break Semi is to hurt her pride, show her she is nothing special. A few chapters later, Nynaeve, who sees Cadsuane as her enemy, swallows her own pride and accepts her leadership in fighting for Rand. Difficult as it is, Nynaeve is not ruled by her pride. Her will power is not bound up in projecting an aura of invincibility. It comes from a core of principles, and this sets her up as Semirhage's true antithesis again.

I'm afraid this is plainly wrong. The thematic connection are very strong.
Here are some more:
Semi embroiders often. Nynaeve sucks at it.
Semi always wears unrelieved black. Nynaeve wears a variety of styles and colors.
Semi has an motherly exterior with a hard core. Nynaeve acts tough, but is motherly inside.
Yet, they both work by bludgeoning away their opposition. They can play political games if needed, but prefer not to.

All valid points. I don't see how Semirhage and Graendal being equal with Nynaeve and below only Lanfear among the FS contradicts this.