Its not easy to handle a rebellious child. As young as she is its obvious what's in her head is already the bad aspect of peer pressure.
Trust me all you guys need to do for her is pray for her that nothing bad happens to her because she has chosen to experience life first hand and not hear say. When the time comes, she will run back home, cry more than she has ever cried before and she will become a better person that you all will be proud of later.
I know her type and mark my words carefully, you guys should just keep praying for her because she will definitely come back home when she realizes that no love outside beats that of family.