What should i do to help my sister?

What should i do about my little brat sister? Shes only 14 but she trys to act like me, or so everyone says. She binge drinks, shes ually active! She wags school. She chats up guys my age (18) who think they're gangsta (you know the type). Everyone says shes going to fall pregnant soon and i dont blame them for saying that. My parents are absolutly useless and dont give a flying f*** about how she acts, they find it amusing actually. And when i do confront them about her behaviour they blame me because apparently im her rolemodel. But i drink in moderation, im not promiscuous and the partys i go to are not out of control rages. I just dont want her to end up like my parents (school drop outs and had kids at early age).