I wouldn't know. I don't presume to have an insight into her mindset like you do. I think it's very likely that she's not right in the head.
You seem very judgmental.
Well of course she was crazy. Crazy with hatred for her husband. That doesn't excuse the act, though.
Using your logic, I can do whatever I want and claim I 'wasn't right in head' or any number of excuses.
You seem very naive.