What can i do to stop a 9 year old's tantrums? from 16 year old sister.?

Well I have some sollutions. okay so ur sister the nine year old is a BRAT! Well when she is on the computer and u tell her to get off and she shrieks slap her. And that should do! When she calls u a name or tells u to shut up call her a cuss word and tell her to shut the HELL up!