Egwene is genuinely surprised because she believed Nynaeve's assertion that the Yellows wanted nothing to do with herbs.

You are trying to make it sound like Egwene is saying "Haha Nynaeve, you are wrong again!" When what she's saying is that Nynaeve would be happy to learn that despite her earlier experiences with Yellows, there is in fact at least one who isn't anti-herbs!

You can argue that Sanderson isn't a good writer because you think this scene is clumsy all you like, but you are the only person on here who has this take away from this particular scene. Perhaps you should go look at the various Mat chapters... they IMO are the places where BS missed the mark.