<human>: Can you condense the text into a few key points?

Pretty much what the title says. I got invited to play a certain game with my friend and her group. I like her and we have been chatting for over a year now. Thing is, I do not enjoy the company of her friends due to them joking about things only their group understands and their general humor style that I don't find funny.  
When I'm with them I'm mostly quiet and I hope the time passes fast. So when I was asked why I don't want to join, I shrugged it off to personal issues. Thing is, I like her and I got a feeling she wouldn't like hearing that her friends aren't funny to me.
<bot>: I don't want to spend time with friend's friends but I don't want to tell her that directly. How to proceed?