Should and can I forgive my cheating girlfriend?

First -- and this is important -- understand what forgiveness is. Forgiveness is when you release (or try releasing) all the anger, resentment, spite, etc. towards someone who has wronged you. You can not force forgiveness, nor should you try. Forgiveness is something only you can do, on your own time, in your own way.

Second, forgiveness and reconciliation are different. If you want to stay with this girl -- if you want to reconcile -- you'll need to eventually forgive her. But you can also forgive someone and say "Bye bye, have a nice life" all at the same time. You can forgive people you disrespect or distrust, and never want to see again.

So to answer your question, in two parts:

1) I think you should forgive your girlfriend, but for your own sake. If you don't forgive her someday, you might simmer in anger for the rest of your life.

2) should you reconcile with this girl? More complicated question. Can you trust her, or will you second guess everything she says and does? Can you get over it, or will you always hold it over her head? If she apologizes, that's a good start. But apologies are only as good as the next action. We've all known people who'll apologize, then turn around and do the same thing again and again. Their apologies are useless.

In short, forgiveness takes one, but reconciliation takes two.

Hope this helps. Good luck.

You should give her a second chance to see what happens. If she ends up in bed with another colleague,with descriptions like before, there's no doubt in my mind that they were doing something. If she was honest though, you don't have to worry about her lying to you at all about subjects like this.
I warn you though, if she's done it once... More likely she MIGHT do it again, but with more than just intimate kissing and hugging. I'd try to be a little closer to her. Ask her what goes on at work everyday, but don't make it obvious that you don't trust her.

Get away from her! No matter what actually happened, she has now effectively ruined your relationship for good. She's not going to change, she will continue to act like this and you are never going to be able to trust her. I know you love her man, but the truth is she's a skank. You need to save yourself and end this as soon as possible. I'm sorry.

NO WAY

you have to accept that its not going to work with this person, and end it. I'm sorry, as its difficult.
But I don't believe this is something that's going to disappear. And trust is a difficult thing to re-establish.