But i'd probably stand back even if i SAW DD in the situation you describe and let her fall unless i could see terrible danger.
I do this too, only do many times I can say don't swing down from the bunks or don't jump off the couch or don't be silly on the scooter... at the end of the day hurting themselves, if it's minor, can be just the wake up they need.

DD has a stuffed toy called Bedtimelamb (bee'emlam she calls him). The other morning she had her breakfast then marched into the living room and, hands on hips, demanded "Where's my bloody bee'emlam!?" Dunno where she got that...
Chase did that the other day, walked into the lounge and declared "Jaidan look at this bloody mess!" I think I might have said it the week before...
However I didn't laugh, I told him it was naughty to speak like that and very rude. One day he came back from my sisters saying F*** and I stopped that quick smart by saying "where's the truck?" everytime he said it (was about 2) and he stopped after a few times. Have to admit I laughed at first, out of shock more than anything else.