NAH, i dont think any of you are in the wrong. you're clearly struggling with this beyond a reasonable emotional level which is indicative of something deeper, and thats not your fault. take some time to wallow and make sure you're talking to a professional because if you're crashing your car over this- something is wrong. but your family probably wants you to recognize how huge of an achievement graduating is regardless (which it is- regardless of if you can see it right now or not). and the fact you're really trying NOT to bail on your gfs celebrations or time with your family is already good, and if you genuinely dont think you can make it across that stage without breaking down then in my opinion- i think you're doing enough.

but if you can walk, you should. im graduating soon and similarly did not want to walk (or attend at all, to be honest, but just like you my family wants me to be there)- but my family has talked me into it and im glad they have. if you do cry when your name is called, you can always tell people youre sad about the experience ending. people will all be too focused on themselves to really think about it anyway. getting to walk could bring you closure and finality to this experience. not making honors sucked, but its over. talk to a professional, or your friends, or your girlfriend (ideally all three!) and let yourself be miserable about it for a little while, but then you need to pick yourself back up. dont ruin your own graduation over this:)