She took a slap like a champ

Oh, that was a real slap allright. I replayed it too and you can see the skin of her face do the squimmy-jimmy after she's cracked. She was a non-actor and they didn't have film to burn, so I guess they decided a slap was easier than teaching her to react to a 'near miss'. I'll bet she had a headache after that scene.

I saw the same thing - there was contact and her face showed it - her jaw moved etc.. Almost as if in a boxing match. In the interview / documentary portion, it said the actress was chosen off the street and was not a professional actress. Maybe that's how the production got away with this scene - that and the year the film was made. I wonder what the exact direction from the director was for that scene. Or was it an accident? Pretty shocking.

My accountant says, "1 + 1, 40% of the time, equals divorce".

That looked painful. There'd be outrage if an actor did that today.