Baby laughing when told no

Ka

So, my daughter does this thing (which she learned at daycare about a month ago) where she is hitting herself on either side of her head with both hands. She’ll also grab at her eye/face. When I tell her no, firmly... we don’t baby talk at all with her, she laughs at me. Literally thinks it’s a game and will keep doing it. So, I started to hold her hands when I tell her no and say ouch, don’t hurt Charlotte. Anyone else’s little going through this? Hoping like crazy it’s a phase?