Sorry but that isn't accurate. While Moraine very likely suspects that Nynaeve has channeled before she has literally no information that utterly confirms it.
While many wisdom's are channelers not all are, and those that can't still say they can listen to the wind (one of the duties of the Wisdom is to give guidance on the weather and crop forecasts, ect).
Since she hasn't witnessed a prior channeling event, nor has Nynaeve discussed with her a prior channeling event, Moraine can only attest to the one channeling event that she knows occurred.
This is a great example of how the Aes Sedai can thread the truth through the head of pin.
This also happens in episode 6 when she is being tried and Lilandrin brings up Nynaeve, and she states she suspected but didn't know.
Moiraine teaching Egwene to embrace the One Power in Episode 2 and her statement that the wind listens to Egwene is entirely predicated on Moiraine knowing three things:
1) That 'listening to the wind' is Channeling (she learns this during her pool cave confrontation with Nynaeve)
2) That Nynaeve herself knows how to 'listen to the wind' (which is not outright said, but is all but confirmed by Nynaeve's story about the former Wisdom's ability to Channel and the knowledge that Nynaeve was raised and trained by said Wisdom, which Moiraine makes reference to during that same pool cave confrontation)
3) That Nynaeve is training Egwene to 'listen to the wind' herself (something we don't see her learn onscreen, but that she would have had to have learned at some point before the Winternight attack)
Furthermore, Sarah Nakamura, a book consultant on the series, revealed that, within the version of the WoT world that the TV show is establishing, a woman's ability to Channel cannot be sensed unless they are actively touching saidar, meaning that Moiraine's conversation with Egwene absolutely could not have occurred without Moiraine knowing that both Egwene and the absent Nynaeve could 'listen to the wind' (Channel) just like the Wisdom who raised and trained Nynaeve, thus invalidating any and all subsequent claims of ignorance about Nynaeve being able to Channel on Moiraine's part as being covered by Ads Sedai double-speak.