Replying to Lil bro's and sis's

Do you guys have little borthers or sisters? I have a little sister adn i just cant keep her in line. Shes 9 years old and when ever she does something wrong she acts like shes too young to know right or wrong. We just got a new $1700 computer ansd she fucks with it as she wants? I mean she lets her 10 year old bitch fried fuc with it. She somehow put a desktop on it a way ive never heard of. I cant even get it off in properties. I gotta figure out a way to straighten this shit out. If it was a little brother, now that'd be a different story. I'd simpl kick his ass.