Well, here again, are we discussing the character or just the film? If we are discussing the character, we get to interpret the novel. If so, in the novel, Tom discusses Michael at length with Kay about Carlo and Tessio, etc. So, she was aware. Again, unlike bot Carmelas, she eventually could not reconcile her husband's actions with her morality.


"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."