I think it's mostly guess work when exactly she found out, not least because Wilhelmine herself is inconsistent about it.

Yeah, I noticed this after reading volume 2 (which I read after Oster). Having suspicions but being in denial would account for a lot.

Thank you for the Graffigny write-up! There were so many fascinating people in the 18th century that I would have no idea about if not for salon. And yes, it is telling how many biographers have trouble when their faves are problematic.