What do I do now?

Arianna
So this girl, she was my best friend for literally 16 years. And now without explaining why she hates me. Like she tried flirting with my boyfriend and told so many lies about me.. And I don't even understand why... And i don't know if I should apologize for something I don't even think I did, or if I should tell her to go fuck herself with a cactus because that's the point I'm at with all the bullshit. I just I miss her Friendship so much, because I don't really have any other Girl friends. I only have my boyfriend and the guys he hangs out with now. 
Suggestions anyone?