She was of another generation and of another culture. Of course she knew. She knew when Vito was broke and could only afford a pear that she should compliment him. She knkew their sudden rise to wealth and power was not exactly on the up and up. When Sonny tells her about Vito being shot in the deleted Saga scene, she very cooly announces she is going to go change her clothes in case she can go to see him. also in the Saga Sonny mentions that she has been through this (Vito being hit) before.

I agree that she laid down the nobusiness at the table rule, as well as the "don't interfere"rule.