I come home with a friend and my girlfriend is eating pussy.

You think your girlfriend is a formal, educated girl and one day you come home and find her with a friend eating pussy and very happy so you are left with your mouth open and you have two options: get angry with her or join that party with your friend and so between the four of you have a good afternoon of uncontrolled sex hehe, it seems that our friends have opted for this second option and I think they are completely right.