Hello I usually don’t Reddit so I don’t know any slangs or anything like that but anyways

I’m 19M and I’m with my one year relationship gf who is also 19 and we basically the same age. It’s been about almost a year since she moved away to another city to go to college and I stayed in the city that we are both from. A few months ago, when she started college, she made friends and there was this one guy who was part of those friends, and we will call him C. She told me that she was getting along with everyone and although she didn’t go around saying she had a bf but that’s because people wouldn’t ask her abt it or they wouldn’t talk about the subject. Anyways all this was past semester so by the end of the semester C had confessed his feelings to my gf and my gf ultimately shut him down saying that she didn’t like him and that she was with me so they stop talking and being friends. Happy ending right WRONG Turns out that recently he came back and in other words he started texting my girlfriend and they talking again and even playing imsg games and all this stuff. I found out cause I asked her what she was doing while in a ft call and she said playing games with C. I instantly asked her why and got mad cause C has feelings for her and she still texts him and gives him attention. The thing is my gf got mad at me for saying that to her and she told me that he doesn’t like her anymore (which I think is horse shit) and that I need to relax. Am I really overreacting??? Idk what to do honestly like I trust her and I know she’s loyal but I don’t like that she’s texting with someone who has feelings for her.

Update: we broke up and now I feel much much better