Is this OUR job to fix this with our son's GF?

No it is not your job to reach out to her. She should be reaching out to yall if you ask me. What normal person would do what she did and see nothing wrong with it? I mean seriously, though. Anyway, I would stop inviting her over just let it go. She'll come around when she's ready don't feel bad about this b/c honestly its not yalls fault. Now if him and her were staying together in their own place then we shouldn't be having this discussion but since they don't. I mean you have to make her respect you or you wouldn't get it. Way to go on that one. As far as her parents their obviously not the brightest bunch since they think its ok to do what she did! The apple does not fall far from the tree. Let it go, don't push the issue of having her come around! Like I said she will when she gets ready. I just want you to know their sitting around talking bout yall. Everytime you invite her over she like yea they invited me but I'm gone show them, believe me. I'm sure you can care less but just a heads up. I'm sure you could care less but I don't think you were wrong!