Hello. Recently my significant other and I got into an argument and I'm not sure what to make of it. I saw that she was Facebook friends with a guy she had a one night stand with 4 months before her and I met (who is a friend of a friend of hers). They have no prior relationship, spent only a couple days together, and haven't really spoken since (only a couple scattered texts after the hookup). I kindly asked her to unfriend him since it bothered me and she became quite upset. She said "that would be rude" and "that's just not how we [not sure who she's referencing] do things." I was surprised since I thought this was a reasonable request, but now she's upset with me and harboring some resentment over the ordeal. This was after she expressed some hesitancy at the idea of become Facebook friends with me. Not sure what to think of that. Thoughts?