FREAKING BACKSTABBER.......?

omg what do i do??! theres this girl in my cl that i absolutely know she is using me.. all my other friends tell me everything she says about me and ive heARD SOME... but ive lso heard that she sys nice things about me.. one day shes like: omg amy is such a freak i hate her.. looser!! but the next say shes like: omg amy is soo nice!! i luv her.. ugh im just thinking evryone in the world does this.. but should i just totally ignore her and me mad?? or what should i do