1 year out of highschool but still caught in dumb drama

I used to be friends with a little miss perfect type in highschool but stopped due to feeling 2nd class around her. Skip ahead some years and she ends up dating my best friend, and all my regular friends adore her. My jealousy in these times are unmatched.I had started fooling around with my best friend which was already a no-no as I was in an LDR with an extremely mentally unwell guy who I did not feel I could break up with. I had told my friends the circumstances in case they had problems with it and we could hash it out. Then, he started dating her. But we did not stop. Everyone involved is young and stupid.Come one day my acquaintance wants me to come to his house. He's still friends with my current boyfriend and sits me down alone, where with Great Urgency he tells me he and all our friends think my best friend has manipulated me and his girlfriend into sleeping with him. And that my boyfriend would be told about the cheating one way or another. It left me reeling, hysterical. It was uncomfortable that all my friends had been secretly feeling this way all along, but there was also the very real threat of suicide from my boyfriend if he found out. It was one of the worst days of my life. He didn't kill himself, but I stayed with him another year. My own circumstance was so dramatic that I never ended up giving that girl any proper consideration. To be honest, I still don't care. At the time it was because she had the support of all our friends behind her, but I've just come to dislike everyone involved.