While it's true a lot of protections didn't exist when this was taking place, what happened to Dee wouldn't even be considered wrongful termination in today's day and age--or at least not in the legal sense.
Dee wasn't fired because she's a woman, or because of her race, or because she's pregnant, or because she's over 40 or because of her religion. Those would be protected under the law; although the diner might be too small and even be exempt from many of those protections.
She was fired because her jerk of a boss believed an anonymous customer over his long term waitress. That mi