She has used this new excuse enough times that it has become a bit funny.
Don't keep turning the lights off and on. ---- I'm just joking.
Don't chase the cats. ---- It's just a joke mom.
Don't dance in the cereal that you just dumped on the floor. ---- It's joking *crunch*
There is only so many times you can request, redirect, and reprove. So sometimes you just got to get in on the joke and turn a mess into play time. Show her where she gets that sense of humor from.