You should ask your girlfriend for help since she is the psychologist.
Empathy can be difficult to understand. The basic idea is to let the person know you understand their feelings, but without telling them how they feel.
Erin had a very good example on her blog about when she was at the post office and the guy behind the counter screwed up a womans business order. Erin was able to diffuse the situation with empathy. I searched for it but I can't find it now.
Edit: Just kidding!
Here it is.