What will i do with my younger sister's b*tchy friends??

you obviously deeply care about your sister and that is respectful but your sister has to make her own choices. The only thing you can do is love her and let her know you're there for her. It's hard watching a loved one go down a road that could lead into serious trouble. It's great you voice your opinion to her and try 2 help her to the right path but remember you can't make her take that path she has 2 want 2 do it. Hopefully she'll learn before she ends up in trouble. If not then continue to let her know you love her and will help her but not bail her out.