Plz... Help what do I do?

So my g/f was off school for a holiday and I had to work. She promised me she was going to come see me at work but then told me she was going swimming for a couple of hours and might not be able to come see me at work. I was off at 6 PM and she had to start work at 6 and we both work at the same place. I left right at 6 and did not see her nor hear from her since. When I went to go pick her up at 10:15 PM I waited for half an hour then the supervisor came out and I asked if my g/f was still in there but her reply was "She did not show up". At this point I was freaking out thinking something happened to her and rushed to her house come to find a guy leaving. My first reaction was "Are you cheating on me?" She said no he is just a friend. Today She text me telling me that she was going to talk to the supervisor because she did not show for work and our supervisor knew about what happened and talked to her. Turns out she spent the day with her Ex. And I am getting a call from my g/f later