I think they were having an affair but I don't really think she expected him to kill her husband. I don't think she gave a crap about old Hemy either. If she knew anything then she is being an idiot. She should be bringing out the tears. I'd be pissed if after all that, my boyfriend caused me to lose my husbands life insurance!
You know, after actually paying a little more attention to what's been said, I think she could have maneuvered him into doing it and then going "OMG I didn't mean KILL him"!