Best friend?

So, my best friend has been my friend for years now. Well this year is the year that I got my first real boyfriend. Things have gotten very serious between me and him. Anyway, I lost my virginity to him and she encouraged me to do it and even helped me set up the place to do it. She kept egging everything I did on and never told me anything was going on. Then she turns around and tells my parents everything about my boyfriend and I and that shes "worried" about me. Things were fixed and we continued on, but one day last week, I was feeling down on myself. And I made a comment that I didnt feel good enough about myself, so she turned around and told my parents I'm in a "abusive" relationship. But the entire time she is telling my parents everything, she is talking about having sex with a guy who has a gf and whose cheated multiple times. I'm don't know what to do, I'm so tired of people lying and going behind my back. And my parents worship the ground she walks on. BTW we are all still in high school....so any advice?