hello, so me (20m) and my girlfriend (19f) have been dating for almost a year now. she called me and told me how she had a conversation with a guy that she used to like, and he liked her also, but they never dated because he told her that he didn’t want a relationship. she ended up finding out that he just wanted to have sex (btw this was about a month before we started dating). when we started dating, she told me about him and told me how he would do nice things for her just for the reason of getting into her pants. so the perception i got from him was that he was an asshole and that she despised him. fast forward to today, she tells me that when she was sitting down, he came up to her and asked how she was doing. she told me that she responded with “oh i’m good, i’ve been dating joel (me) for almost a year now” (which the guy already knew because we were friends since elementary school and had a lot of mutual friends). then she walked away. i got upset in the moment because she spoke to him regardless of what she had told me about him. i wish i had kept my cool in that moment, but i didn’t. after we hung up, i called my friend who had the guy’s number. i then texted him and told him not to speak to her. then he called and told me that the conversation was mutual and they talked about more things than what my girlfriend told me. my girlfriend lied about what they talked about, which raised red flags. when i confronted her, she said it was because she knew how i’d react and she knew i’d be upset, so she lied because of me, which baffled me. i then broke up with her because i’ve been through too many relationships where a girl has lied to me about something involving a guy, and at the end of the day it was true. i want to understand where i went wrong and where she went wrong.

p.s at a point this relationship she got upset with me for accidentally looking up a girl i liked instagram, and i understand where she was coming from but, she says she doesn’t fully understand why her having the conversation instead of walking away rubbed we weird.