<human>: Give me the gist of the text in a nutshell

Last year I hooked up with a guy who later joined our friend group becoming one of my best friends.  I really liked him but we never got together again.  

My best friend who had a long term boyfriend when we first got to know this guy has since broken up with her boyfriend and in November had a drunken fling with the guy.  The problem with the situation wasn't the guy she had gotten with but rather that she was the one person I had disclosed all my unrequited feelings about him to.

The following week we had a long talk and she admitted that she had been worried all weekend about my reaction and was really sorry that it had happened.  I asked her straight out if she liked him and if she did that she should go for it. I want her to be happy and if he makes her happy then I'm all for it. What I don't want is her casually hooking up with him as it makes me feel like a piece of shit.

Lately I've started to suspect that they've hooked up again and everyone knows about it but me which makes me feel physically sick.  I don't like him in that way anymore but I don't like the thought of everyone laughing at me behind my back and keeping it from me.

Yesterday I got confirmation that they hooked up again a couple of weeks back but no one knows that I know. I don't want to be mad at my friend but I can't even look at her without feeling angry and upset! I feel so betrayed.  I want her to just tell me it happened so that we can discuss it and move on.  Should I bring it up or just try to forget about it? I don't want her to think it is because I like this guy, rather that I am hurt that she would do something twice that she knows 100% would hurt me.
<bot>: Best friend hooked up with the one guy she shouldn't have and I'm scared that I'll let it ruin my friendship with her.  Has anyone any advice on what I should do?