My 5 year old DD has been acting out a bit lately. Like yesterday she pulled the cat's tail, hard, with both hands. Or the other days she hit her brother in the face. When trying to talk to her about why that's mean, why we don't do that, etc she just smirks and laughs and doesn't seem to take what we say seriously. This has been happening more and more, and honestly drives me crazy. How would you handle this?