My Fiance And I Have A 16 Yr Old Daughter.

My fiance and I have a 16 yr old daughter. She refuses to stay home and has been out of our house for over three months now. She refuses to follow any rules, go to school and has become a very untrustworthy person. For the past four months she has lied about being pregnant and post pictures all over social media of her "belly", even wanting to name the child. It is appearing as though she is believing all of her lies and lying has become a profession for her. Any ideas?