Thoughts on the situation?

Savannah

So I have this friend. She was my best friend. We literally did everything together. We would talk about anyone and anything, good and bad. So there is this guy, he is my best guy friend. I do not at all like his girlfriend. I was getting so sick and tired of her so I decided to rant about her to my "best friend". I was saying she annoys me and she treats my guy best friend bad (slaps him all the time for no good reason) but then I was basically talking crap about this girl. (Please note the my best friend hates this girl just as much as I do. She talks more bad about this girl than I do.) Anyway, I was saying that she isn't special and I could take her boyfriend if I wanted to, you know, stupid petty crap. My best friend, decided to screenshot my messages, cross out the parts where she was agreeing with me, and send them to that girl and her boyfriend. I never knew that my best friend of 6 going on 7 years would backstabbing me like this. She literally pretended to be on their side. She is so two-faced I might as well call her Harvey Dent. I always trusted her no matter what, kept her secrets, lied for her, and this is what she does for me. I just spent $100 on her by taking her to the fair, and this is how she repays me. What a bitch. Any thoughts on this situation? (Also note, I know I am in the wrong for talking about someone behind their back, but it isn't the point of why I am posting this, the point is that I trusted my friend to keep a secret but she broke my promise.)