Growing up

We were driving home from dinner tonight..I was in the passenger seat so I could turn around and talk to M. The conversation was pretty standard (a few knock-knock jokes, a few Dora or "M" stories created by me etc.) But then I looked back and M was picking her nose...for the nth time I said, "M, please don't pick your nose..use a Kleenex. It's disgusting!" Her usual response is "I don't need a Kleenex" and she quickly removes her finger. Tonight, however, my quick-witted child quipped "Then don't look!" I almost died laughing (maybe not an appropriate response, but I couldn't help myself)!!! How did she get to be so grown up!?!?!