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

So I've been dating this girl for about 9 months now and recently she sent me a message at work and something I had not noticed before was that the mobile version of the facebook message interface shows you their last active time stamp down to the second. Well anyway after I discovered this I started to monitor it throughout the day which in hindsight was probably a bad idea as it has raised some flags for me and I'm not sure how to approach it the correct way or if I should even bring it up. She works from home so she has quite a bit of freedom to do as she wishes so I'm seeing her active sometimes for up to an hour at a time and it really has me thinking that she's talking to anohter guy. Of course it could be other things but it just seems like a lot of time to spend just browsing facebook. Not only that but the way the activity shows falls in line with a chat conversation. I'm hoping it's nothing and aside from that everything seems normal. Just would like some opinions. I've asked her breifly in the past and she said she talks with some people but not "chatting", just a few messages here and there and says they are just friends and I have nothing to worrry about.
<bot>: Girlfriend spending a lot of time on facebook while I'm at work and I'm concerned she is talking to other guys. Should I even be worried or bring it up?