How do i get my younger sister to stop watching inappropriate tv?

I just want to know how to get my little sister to stop watching bad tv; like mtv. She is 13 and I am 16. She is very impressionable. She does everything her friends do like buy the same things and dress the same as her friends. It annoys me but i also think it is bad for her. She never listens to me and my mother usually lets her do whatever she wants. I am concerned that she will be like these girls on tv if she keeps watching it. She wears low cut shirts and really short shorts. i don't know wear she gets it because i never dress like that. I barely wear makeup and she puts a lot on and so do her friends. She told my mom that she didn't want to go to collage and i just want her to listen to me because I think that i might be able to help her if she listens. I do not want her to ruin her life. I walked in on her watching mtv and i told her that if she turned out like those girls to never talk to me. I was really mad and she was being a smart *** and said " well what channel is barney on then?" Can someone please give me some advice? Sorry this is so long. Thank you.