Do you intervene if your kids are hitting each other?

⚪Hula👶👶👶 • left glow for a break. I may come back as some point but for now its taking too much of my time
Okay I am at a loss with this one. I have an aqaintence who will let her kids slap each other and make each other cry. If I point it out she waives it off and says its 'kids stuff'. I'm not a parent so I'm not in a place to offer advice on how she should handle it. What should I do? My local CPS does not handle things like this - I didn't report her, but I have a friend who's a social worker here.