<human>: Can you provide a brief overview of the text?

My gf(21) of over a year just told me, her bf(20) that she was out walking with her son and stopped to talk to her neighbor. She then told me that her neighbor and her had a "thing" in high school. I'm not so much bothered by the fact that they had a thing, but by the fact that I hadn't known about it whatsoever in an entire year not to mention the blatant hypocrisy going on. I went to my niece's dance recital and saw a girl I had dated and been with, no words or even eye contact was exchanged, and because I try to treat her how I would want her to treat me, I told her I saw the girl. She immediately started asking if I had talked to the girl or found her attractive etc.. Well she tells me that she talked to this guy and is super nonchalant about it, like there should be no reason why I'm upset. And then when I tell her why I'm bothered, she tells me "I knew it would be a problem.." I tell her it doesn't matter and she asks for more so I tell her. She responds with "have I ever done anything for you not to trust me?" I tell her what bothers me a few more times and I get no where. She then begins to turn the blame on me saying "Just nvm ill continue to have no friends."

Is it wrong of me to be upset/am I overreacting about this? I don't care about the "thing," I care about the hypocrisy and how she doesn't seem to care about how it upsets me. Am I wrong in this? Am I being too sensitive?
<bot>: Gf just told me she was talking to a neighbor she had a thing with. She gets upset if I even see someone I've been with. Am i wrong in being upset?