Thanks for all your replies
I thinks it is the right thing for me to meet the girlfriend, no question about about. I totally understand that she would want to meet me in order to remove the stuff going on in her imagination. I also understand that she needs to make sure that I don't want to steal her boyfriend away from her. I can say this is really not an issue at all, because as much as I like him he doesn't touch my heart in that way. And I have made this very clear to him.
I sense a lot of guilt in him. He told me he had some feelings for me, and that was something he said he wouldn't tell his girlfriend. I don't have similar feelings for him and I get the feeling that he thinks that he will feel less guilty if i met her. The pushiness triggers resistance in me because I feel he doesn't understand that I too am a person and I need to do things in my own time. It is totally unfair if they have to set all the rules, and I also feel I showed I am willing to meet, but that I need to take smaller steps..
Last year I was also seeing a guy who had a girlfriend, and she wanted very much to meet me very quickly. I met with her because I felt it was the right thing to do, but I wasn't ready yet, and when we met I think she sensed my resistance and after that she was extremely jealous. So i do think there is such a thing as meeting someone to soon.