How can I help my 11 year-old sister realize she doesn't need to act slutty & mean to get attention?

Okay, so my youngest sister, let's call her Molly, is acting like a grade A b-i-t-c-h. She dances dirty in public, curses, hits people, talks sexual, and acts out some pretty graphic scenes. I try to help her, but she ends up making excuses & I get mad & I just blow up knowing it's not the right way to handle things. She is starting to be really mean towards me, my mother, my middle sister, and even teachers, anyone that would help her, but she'll be nice to someone who turns around and treats her like crap. How can I help her understand she's going out of control. We have grown up in a super strict, religious household that we both want to get away from. My middle sister, we'll call her Rose, doesn't, but instead of helping Molly, like our mother, she just gets really mean towards her & calls her a whore & stuff. My mother has called me & Molly whores & sluts many times for wanting to break away from a religion that dictates what we wear, what we do, & basically everything, but she isn't doing this in the right manner. Breaking from a religion isn't the same as turning into someone she's not. My baby sister isn't like this. I understand how she can think this because she models how she should live outside of our faith from movies & romance novels, whereas I base my life from my friends who are super supportive. I'm trying to be supportive, but I can't if she's pushing me away.