There is no way she didn’t know, come off it. Plenty of people knew, including higher-ups in management. All this “we were so shocked to find out” is nonsense, and I don’t think anybody is buying it.
I mean people are married or related to people who do unspeakable things, without knowing about them.
So she can be best friends (or however close they are/were) with him without having known about what was going.