Don’t know if I (23M) should break it off with gf (23F)

So we met in college and have been dating for a little over a year, she’s also my first girlfriend. We have a very good relationship and have only had a couple biggish problems. She is very extroverted, whereas I am quite introverted. She goes out quite often and sometimes (but rarely) stays at her friends or teammates house. One night in particular however she stayed over at a guys house after the bars. This is a house with people from the men’s team of her sport. One guy in particular she was hanging out with. She came back the next morning and said she fell asleep on the couch soon after she got there. I said okay and moved on, until a couple of nights later. During the weekend she said she was going for a ride to talk with a friend, and she said it would only be around the block and for a couple of minutes. She said who it was (the guy) and they proceeded to go to his house and she didn’t come back for over an hour. I questioned her on this and she said that nothing was going on and they just talked. When I asked if something really was going on she just said “just not the vibe”. She doesn’t talk about him really unless I bring it up. Pretty sussed, I checked her Snapchat sometimes to see if there was communication. And there is frequent communication, often late at night. I’ll see missed calls from him on Snapchat that she does not answer. I need help on this because I really feel like I can trust her and she seemed honest. She mood and sex drive have also been down as of recently but that is probably due to her switching bc. It does seem very strange though and I am teetering on the edge of breaking up with her and being with her for a long time. Any advice would be helpful.

tl;dr Unsure if my girlfriend is cheating on me, I don’t think she would, but I have a bad gut feeling.