I would fix her with a firm glare that says "I know what you did". He should have dropped her off first and in future I would insist that hubby not be left alone around this woman. The fact that this was done in front of her child really bothers me. It shows further that she has no respect for boundaries, and no regard for anything other than what she wants.

Don't, whatever you do blame yourself! You didn't do anything wrong. He told you about it and that is good because now you will know to protect him when she's around. I'd tell Auntie that her friend is a cougar...