How can i shut my sister up?

my little sister is always buggin me (shes 3) and i cant take it anymore and at school theres this f****** retard that will tell when u basically did like nothing so my life is really a nightmare.my little sis is SUCH a crybaby (example)she hits me and then she cries also she always follows me and my friends and spoils the fun i litteraly wanna beat the living **** out of the guy at school and my sisPLZ PLZ PLZ PLZ HELP!!!!