This is my first ever post so apologies if I'm doing something wrong:
I (M21) dated a girl in high school for a couple of years and we broke it off due to things not working out and us wanting different things. We later became FWBs, as we both wanted a sexual outlet until one found someone else. We had agreed to let each other know if we did anything sexual with anyone else. I was on a trip, and made out with a girl at a club, which we talked about and she was fine with. We slept together a few more times and everything was fine. She lives far away on her own and whenever she'd come back, we'd do stuff.
But recently she told me that she had unprotected sex a few times with a neighbour who was moving away last month. She even let the guy cum inside her. Now I know we're just FWBs, but this stings, and I'm not sure if I can do stuff with her again. I don't think she's in the wrong at all, but I told her I don't think we should do anything or see each other again. We were good friends before, but I'm not sure if I can really talk to her without hurting. Am I just overreacting? Is it rude to just end things all of a sudden, despite knowing her for over 7 years? What should I do?