<human>: [for the mods we have been dating for one year]

So I just logged on facebook on my ipad and without realising i opened an inbox thinking it was for me. Now I only realised it was for my gf after i had opened it. It was from a new guy who she had been speaking too since my birthday. (wednesday) Now these two have really hit it off by the looks of it and in the messages they keep going on about wanting to meet up and how they're so glad they're talking.
  if anyone cares there is a short screencap of the convo.

Now instantly this has made me pissed. My girlfriend has been constantly ignoring me and spending a lot of time at home recently cause she is "too tired" and enjoys been with her parents and dogs. But what has annoyed me is that she is sad when he seems to "ignore her" when she constantly ignores me! They want to go for drives together to chill and now it feels as though i'm being put 2nd. I've had enough and when she finishes work in a few hours time I'm going to be waiting outside to ask wtf this is all about. Please help with what would be the best way to talk to her about this and how I should end it. (this is my first serious relationship so I'm a little bit of a novice)

Can you give me a shortened version of the text?
<bot>: accidentally found a very flirtatious chat between my gf and a new lad. Planning to confront her in a couple of hours when she finishes work. Need urgent help please!