<human>: I've been casually seeing a girl for two months now. We've both admitted that we really like and care about each other, but don't want a relationship in our lives right now.

Three nights ago, she and my best friend hooked up at a party. She also gave him her number. While I'm okay with her hooking up with other people (I do the same), I'm incredibly upset right now and don't know what to do. They claim that they didn't remember who the other person was (they met once for 5 minutes before this).

I know I don't have a right to be angry, but that doesn't stop the fact that I'm very upset about this whole thing. I don't know how I could ever be in the same room with both of them again. Whenever I see my best friend, I always think about him kissing this girl. She slept over two nights ago and I couldn't fall asleep or feel intimate because of this.

Is there any way for me to get over this, or should I call the relationship for good?

Can you provide a brief overview of the text?
<bot>: My best friend kissed a girl I've been seeing casually for a while now, trying to put this past me but not sure how.