I don't want my sister to go to highschool with me!?

hi so my names Shelby and I'm 14 and I just finished me 9th grade year at my highschool. now I'm goingto be in 10th grade. My sister is going to be in 9th grade this year and she's going to the same highschool as me. My sister is SO annoying! She always tries to hang out with my friends and she always tells them embarrassing stuff about me that aren't true. She's so embarrassing !): And I'm also afraid of her finding out that I don't really have that much friends.. She might make fun of the fact that I don't have much friends.. We just moved that's why I don't have alot of friends right now, but I'm trying.. My sister is SO embarrassing and she always makes fun of me at school.. What can I do? And there's a chance we mitt fight, like hair pulling. She can't control herself and she always fights with me! Making me look bad.. What can I do?