My friend is changing for the worse ?

my sister seems to have gone a bit like than too :( Dont just tell her that she seems fake (I did and My sister got realy mad at me ) my sister messes around in lessons and goes round with people who drink and smoke and she gets mad at me when I overhear things about who smokes and she can get quite nasty I would say just to leave your friend to it because she seems to want that style of life because she is faking it, she does not seem to be changing for the better but Life goes on , worry about yourself and every thing should work out :)