>>253300isshh, thats tough man, i am glad i dont have sisters
you will have to be clever, some reverse psychology type shit, if you go to "oppress" her, it will only backlash even worse. Somehow facilitating to her the reality of that world, that is a bunch of no life losers, but without making it a guilt trip or a dad lecture.
Find a your most loser friend and go with your sister to the shittiest place possible, try to make her have a bad experience around that shit, not like getting her rape, but close, take her to a place full of lowlifes that call her names and shit,
maybe after that she'll gain some sense.