While I was visiting my parents, my sister, brother-in-law and nephew came round for a meal. During this meal my sister and her husband had a minor disagreement and she slapped him on the back of the head to make a point. Not particularly hard, but it wasn't done as a "joke" - she was clearly cross with him.
I don't feel this is acceptable simply because it was a woman hitting a man rather than vice versa, and also think it's a very bad example to set their son. I'm assuming that this is not the only time she has done something like this. Should I say something, or keep well out of it? I have mentioned it to my mum (who was there at the time, so it wasn't "telling tales").
My sister and her husband seem to have a close relationship, but she is often complaining about him or berating him for various perceived transgressions. I'm sure he's far from perfect, but from the outside he seems a pretty good husband and father who is reliable and hard-working.