<human>: I dated this girl for almost 1 year and we decided to call it off about 3 months ago. However, we sort of became FWBs for a couple months. She told me last night that she fooled around with another guy a day before fooling around with me earlier this week. I can't really consider it cheating, seeing as we weren't together, but I can't help but feel betrayed by her actions. I'm having a lot of difficulty getting over it and I can't convince myself that I need to move on. She is saying now that we are better off as friends and that she wants me to be a part of her future. Should I brush her off and move on, or should I be welcoming her as a best friend? Will that only further complicate the situation?

Can you condense the text into a few key points?
<bot>: is it considered cheating if an ex-turned-FWB fools around with another guy? and should I be hurt by it?