My supposed best friend talks about me.?

What should i do. She talks about me behind my back and then today she gavr best friend bracelets to my other two best friends and herself. There wasnt another for me. I am the only reason why she has a sicial status and she knows that, that is why we are still friends. How should i tell her i dont wanna be with her. I was thinking if going up to her and saying nice necklace or maybe so wheres my necklace. Suggestions?