best friend betrayal

Okay so there was this guy who was massaging my innocent best friend, and he was asking for nudes and so my boyfriend offered to message him to tell him to back off and he did so and so then my best friend wanted his Skype to say thanks so we did a three way skype call and What happen is that my boyfriend and I thought that she liked him so I was listening in and my best friend thought I went to do something and then she said all these horrible things about me and told him some things that are just horrible, she said to him that I would cheat (which I would never) and that I sext loads of guys (nope wrong) and I'm a Virgin so I'm far from a slut, i havt even touched a dick nor has a guy touched me that way and she said that I get loads of dick pics and that I'm a slut and that I would end the relationship with him bc I would get bored of him like I did with the other guys and like I left those guys bc they didn't respect me and they bullied me and treated me bad and she knows that.  He then pretended to flirt with her to see if she was a loyal friend and she flirted back sooo much, so then she said some other mean things and I was crying all night to my boyfriend bc I trusted her with my life and she betrayed me, and so then I forgave her. And then she started manipulating me saying she will like get with him if I don't do things and I'm like wtf and so then we argued and I forgave her and then I was getting her a date with a guy she really liked and she back stabbed me by screenshotting our messages and sending them to him so then he didn't want to date me but he asked me out and she got really really jelous and of course I did no and she made it sound like I said yes to my boyfriend and honestly I don't want to loose her as a friend but I feel betrayed and I don't know what to do about this situation, I'm just glad I have my boyfriend who understands it, does anyone have advice?