What was the basis of the scolding? Was it related to the indiscretion in the previous year, or was it work related, or what?
As an employer, if my wife had an "almost affair" with one of my employees, I would deal with my wife about it, not the employee. Especially if she were the one who instigated it.
If your boss fires you for a momentary indiscretion with her husband, then that is probably wrongful termination. If she hounds you about it, then it's harassment, for sure, as she's creating a hostile work environment for you. This, compounded with the fact that her issue with you has nothing to do with work, puts her in some trouble.
My advice, however, would be to resolve the issue with her, or find another job. No matter how much the law is on your side, it's not going to make working for this person much fun. I know it's unfair, but, hey, what can you do?