<human>: Could you distill the essence of the text into 1-3 sentences?

We've been dating for 8 years. So I don't know if this is just me being a little paranoid or if I am in the right here. My girlfriend started working at a new job about 5 months ago where she ran into an old male friend who now works with her. At first they just talked a bit, than it turned into a daily visit to each other at the end of the day, than they started texting and facebooking each other. She occasionally would come home with gifts he had given her, nothing big, just small stuff. It got to the point where people where they work thought they were dating. 

So this all made me a little uncomfortable and then about 2 months ago, I was using her phone to text some friends to go out for dinner when I saw he had sent her a text. I opened the texts they had exchanged together (I know I shouldn't have) and in there was info about how they had gone out to lunch together. She had never told me they were going out to lunch or anything. (It was on a day she had off, so it wasn't a work lunch or something of the sort) 

This led up to me being too uncomfortable with it and I brought up the subject, she just kind of wrote it off at first and then after about 5 minutes of discussing it gave me a "Fine, I just wont hang out with guys anymore" snappy response. Since I brought it up they went from texting each other daily, to no noticeable communication at all. So now I am wondering if they stopped talking, or moved it to somewhere I don't know about.

Sorry if this is written terribly. I'm not known for my strong writing skills.

Reddit, am I being paranoid or is this something I should be worried about.
<bot>: Girlfriend gets close with co-worker, goes out with him without me knowing, than gets snappy when its brought up.