I am not kidding!

I just told Scarlett to put something down and to go to her room, and she said to me, in a very irritated voice, "I was going to my room, GEEZ!" So I spanked her. Then she went to her room until I could come talk to her, the standard procedure. I walked into her room and she said, "Mom, I was thinking, I don't think that you realize that I know the difference between right and wrong." then SHE said, "I was like whoa (in a teenagers voice, complete with mounds of attitude)), she (me)does not even know that I was about to put it down and go to my room." How do you parent a child that at 5 thinks you have no idea what you are doing?