She's like, “Should I step in? Nah, they'll tire themselves out soon.”

More like she was about to smack them, then realized she was being filmed and didn't want to explain the video to KPS (Kitten Protective Services).

Yeah, a visit from the Purr-lice wouldn't be fun for her

I'm surprised they've got so much force behind them too. Those kittens have got paws!

Kind of sad, because that's pretty much how the runt gets decided.

When I was a kid, my cat had five kittens. She had more than enough nipples for all of them, but the four bigger ones would shove the runt out of the way and not let him feed. The mom would lie there and let them eat for a while, then decide they were done, just stand up, shake them off, and walk about three feet around the corner — out of their sight, but where she could still hear them just fine. The four that had just been eating would sit in that spot crying for her to come back, refusing to move. The runt would get up, follow her, lie down, and nurse. And she'd just stay there and let him go as long as he needed. She never cut him off like she did the others. It amused me.