Doesn't help much since I don't know your standing in school...Lemur_Ninja said:As of now, she is a freshman at my school.Aby_Z said:Just say no. Ever take D.A.R.E.?
You have no obligation to take her anywhere, and if she steals your stuff, get your parents involved or just take it back. You don't have to hit her, you can just either go into her room and take it back, grab it out of her hand, or take something of hers as collateral.
Tell me, how old are YOU? If you're in a different school than her, then there shouldn't be a problem with her telling rumors. Also, you shouldn't really care what her friends think, as you don't have to have anything to do with them.
I've found, as the youngest child with a (formerly) bitchy older sister, discipline makes you better. Make her pissed off at the very sight of you. Make her hate you. If you do that, she'll be a better person for it. Also, you can become her friend after you're off to college, if you would really like to.
If you're worried about her rumors, you can just tell your guy friends "That rumor was started by my sister. She's a brat/*****/insert insult here" and they should understand. If you're worried about girls not liking you for it, well you're going to have to deal with that when you try to make your move on a girl. If she mentions said rumor, just say something along the lines of "My sister started that because I wouldn't take her to taco bell" or whatever the stupid, trivial reason is.