Yes, Canada. No, to the employee at will.
If you're a provincial employee, you would get at minimum 1 week severance for every year worked for unlawful or wrongful termination, a federal employee can expect a two week/annum severance. You can't fire someone without just cause. I can't see a potential affair in the mind one party every being construed as a lawful firing..
In Canada you can't just fire someone. You have to have a paper trail. Most jobs have a three month period at the beginning where you can be fired outright, but past that point you have to go through the steps, warning, day off with-out pay, written documentation, sign by both parties. Unless, you want a potential lawsuit.
Again, from what I've read the evidence was slim pickings. And the issue was gender, but there were other factors, like the wife was jealous of a younger, prettier woman. Were the other employees old, unattractive or male?
Was the employee aware that the wife was jealous? If the wife was jealous, why did the dentist write the employee a week before he fired her? If your boss wrote you, about a personal matter, would you write back? I agree, there were a few inappropriate comments, but the majority were not? How would you as an employee handle the situation any differently?