Nynaeve was really into overcompensating at Wisdom. That's the kind of job, which as Moiraine points out, usually goes to women much older than she, like 40s at the earliest. She got the job at 18. So even though people pretty much understood that she could do the job and respected her abilities, they still could not help treating her like a young, inexperienced person. There is simply no precedent for such a thing. The very name implies experience and other qualities at accrue over time. But even though the skepticism and second guessing might be understandable, Nynaeve still had the responsibilities of her job, which included the health of the community, and to a large extent, their economic well-being, since she was in charge of giving farmers their weather reports. Her job and her responsibilities required people to listen to her, and she was usually right, thanks to certain advantages the mundane type of Wisdom did not possess, but people were still inclined to doubt her. Nynaeve had to come on strong and had to be abrasive, and never give and inch, and leave no doubt about her authority, because if she let them get into the habit of disobedience or ignoring her, people could starve or die, and it would be her fault.

We will see this sort of thing repeated in Egwene's storyline later on, with a lot of the same principles of leadership laid out. This of course makes it that much more galling when Egwene criticizes Nynaeve saying that if she fell into a pigsty, she'd try to make everyone think she did it on purpose. Duh. Because if they think she's a klutz, or a spas, that's more reason to blow her off or take her less seriously. But if she had a reason for it, which ordinary people can't understand, that might add credibility to her mysterious sources of knowledge. And when Egwene makes that assessment, it is in regard to Nynaeve having to deal with the Wise Ones, who were trying to force her not to use Tel'Aran'Rhiod. A simple list of Nynaeve's accomplishments in that area from that point forward will show how utterly stupid that was of the Wise Ones. When it came to T'A'R, they were as hidebound and inflexible as the Aes Sedai were about all sorts of other developments. Nynaeve implied by omission that she figured out what Ronde Macura was up to, because she was trying to keep up the facade of competence, to prevent the Wise Ones from cutting her off from whatever crumbs of advice she & Elayne might still be able to get, because short of gentling Rand at that point in the story, few handicaps would have been as disastrous for the cause of the Light as banning Nynaeve & Elayne from Tel'Aran'Rhiod that early in tFoH.

This is true with most things for which people criticize Nynaeve - there are very good reasons, and she isn't nearly as contradictory or hypocritical as people like to make her out to be. In the 2nd through 5th books, she is far and away the most competent and accomplished of the so-called Wondergirls, with Egwene only a member of that group by association, and Elayne not much more so.