he cheated

i’m in an almost four year relationship with the man i plan on marrying. He’s the other half of me, is always there for me, making me feel good about myself, all that. My family adores him as much as i do. Last december, i let him go out with some friends. The friend who picked up was talking to this girl, they ended up to go to her house to “only get alcohol” well long story short, my boyfriend got “completely drunk” and cheated on me. She gave him head, he doesn’t remember it and nor did he cum. it’s just we’ve dated practically forever and even before we were committed we talked on and off for two years... he knows how i’ve felt about my body, i’ve always hated it. i still think about this constantly and even have dreams of it happening again. i love him with everything in me.. Recently we’ve been happier than ever and it hasn’t came up to me as much. Tonight we are going to a party and she’s going to be there. idk how i feel about it or if i should even go. she is TERRIFIED of me, and does not even look my way if she ever sees me because i’ve went crazy on her after the night in december. But at the same time, i didn’t know this girl well before December happened. we didn’t follow each other on social media anything. she says she didn’t know we was together and he didn’t mention me. but still i mean come on? she just met the guy that night and gave him head?? like okkk. i just need someone to talk to about all this and get it off my mind.

edited : no i don’t just blame the girl, trust me i jumped his ass and told him how disrespectful it was to me, and made sure he realized never again. I know it’s not just her fault, it’s his too. And yes, he doesn’t drink anymore nor hang out with that friend. I didn’t post about this girl but she made posts about me and how “i can’t keep my man wanting me”. She’s made up rumors about my friends boyfriend too and tried getting them to break up. do i go to the party or not, idk it may destroy me. seeing the girl and everything and maybe everyone be drinking :(