3 yo peeing on the floor to punish us

I'd fight it with humor. She's trying to make you mad, so give her the opposite. Very overly-dramatically and in a friendly tone I'd say "Oh my gosh, you peed on the floor! How silly! What if we all peed on the floor? Maybe I should start peeing on the floor? It sure would save me the trip to the bathroom!" Then I'd clean it up and walk away without another word about it. She'll probably do it a few more times to test you, but if she's not getting the reaction she's looking for she'll stop.