bestfriend fucked my ex

My ex and I still talked after we broke up because he was a nice and funny person. He tried to be with me again and I caught feelings for him. I introduced him to my bestfriend and we went over to his house one day just to chill and watch Netflix. I discovered that we weren't meant to be because our circumstances just wouldn't work out. He didn't seem to understand so he just cut me out from his life completely. My "bestfriend" told me she still wants to hang out w him after he cut me off and it aggravated me but I got over it because I love her and they were just friends. Today she hung out with him again even though she knows it annoys me and turns out they fucked. She told me this after telling me what I shitty friend she was. I'm feeling a mixture of emotions including shocked, mad, upset, and heartbroken. I don't even care for him anymore but I did for her. I trusted her with my life and now I don't know what to do. She's not even sincerely apologizing. Should I cut her out of my life? Advice ?