I NEED ADVICE!!

Alr so me and my boyfriend broke up like a week and a half ago. (We got back together like 4 days later and we are still dating rn) but as soon as we broke up my bsf decides that its okay for her to talk to him still even tho him and I were on bad terms. I found out she told him she wanted to hug and kiss him, she called him baby, they always called, and she developed feelings for him. Did she ask for my permission? NO. Would I have gave her permission if she did ask? NO. She knew that I still had feelings for him and me and him we actually talking about getting back together anyways. ALSO, SHES THE ONE THAT TOLD ME TO BREAK UP WITH HIM IN THE FIRST PLACE. SHE TOLD HIM THAT I SAID I DIDNT WANT HIM ANYMORE AND THEN SHE TOLD ME THAT HE SAID THAT ABOUT ME. WHEN NEITHER OF US SAID THAT. I actually cannot belive she did any of this. And it was all behind my back. She didn't tell me any of it. 3 days into her liking him, she tells me during my 6th hour that she was gaining feelings for him. I legit cried the rest of that day. And I dropped her. After like a week or so of them talking (he was talking to me too that whole week, he made us both think that we were gonna date him, aka played both of our hearts) and then that night he decided he wasn't going to go for her and then went for me. Also SHE TOLD MY EX (my current boyfriend) THAT SHE LOVED HIM. ARE YOU ACTUALLY KIDDING ME?! Then once he made his decision, she calls me crying with her bestfriend saying that she is so heartbroken. One, I dropped her. And two, karma is a b****. She also told him that everything happens for a reason and that I deserved to get hurt like that. And that was while we were bestfriends. I've never met someone so fake and the sad thing is, we were bestfriends for 3 years. Please comment some support or advice. I kinda need it rn tbh i cry every day over how bad she hurt me. Like im still in pain even tho I'm dating him. I've never been backstabbed/ heartbroken by a bestfriend like that. And also, she tried using "the heart wants what it wants" as an excuse🙄. So yeah, please comment some support and advice, I need it because im still crying and I'm so hurt so yeah thank you! :)