I think it may be a good idea for me to chew my sister's arm while watching this movie.
Why do you want to chew on her arm?
Well she is chewing my arm while watching. This has been interrupting me.
It is okay to be upset that she chewed on your arm but you shouldn't chew on her arm to get revenge. It would end up with her doing something back and then it will never end. Just tell her not to do it again.
Nah, I'm going to go chew on her.
It is not going to help teach her not to do something if you go ahead and do it as well. Really try to be the mature one in this situation so she realizes that she needs to think before doing certain things.