My best friend's girlfriend hates me and I'm not sure how to change it.

When I (18f) FaceTime my best friend (18m) and the girlfriend is there (19f), she will grab his face and make out with him whenever I speak. She has also taken his phone from him and used it to message me. She sends me photos of pictures of us in his room saying "I know about this". I tried to befriend her, hoping that we could come to an understanding but she told me that I'm an idiot and my best friend probably thinks the same. When I called her out, she immediately back tracked. I've considered talking to my friend about this but I don't want to cause drama.
tl;dr My friend's girlfriend has taken his phone to message me and called me an idiot and then tried to claim she didn't when I called her out.


Source.