Am I, a 24-year-old guy, overthinking my girlfriend's comments?

I recently had an uncomfortable interaction with my girlfriend, who is 24. While I was on a work break, I called her twice in a row—something we often do. She eventually called me back after the missed calls, and I overheard her tell her friend, “Oh, let me pick up. It’s my boyfriend. He probably checked my location and thinks I’m cheating on him since I’m at this random building.” I found that comment pretty disheartening, although I understand she likely meant it as a joke. Still, I believe some topics shouldn't be taken lightly due to the impression they can create. If I were in a similar situation with friends or family, I wouldn't feel comfortable making such a joke about her, especially since her friend only met me once briefly. After hearing her comment, I expressed my feelings and asked her why she said that. She told me it wasn't a big deal and didn’t warrant such a reaction. I replied with, “Okay, buddy, I'll let you do your thing,” and hung up. Work was busy, and I wanted to avoid letting my emotions get the best of me, so I chose to step away without escalating the situation. When she called back, I declined to answer. I sent her a text that said, “You’re busy, and I’m busy, so no worries, love.” She replied, “Okay, well then I’m busy tonight too, so have a good night,” which I took as a petty jab since I know she didn’t have any plans for the evening. I also reiterated that I didn’t appreciate her joke. She responded with, “I don’t want to speak to you today. Don’t contact me.” That response was more frustrating than her initial comment. We’ve always agreed on the importance of open communication about our grievances, yet instead of engaging constructively, she brushed it off and seemed to use my annoyance as a reason to be petty. I believe she struggles more than I do with reflecting on her behavior and offering apologies. It used to be the other way around for me, but in the past few months, I’ve made a conscious effort to take responsibility for my actions, even when I don’t think they’re a big deal.