.
Hi Carebear and welcome to SR . . .
I hope you don't take this the wrong way but I'm not sure I would want to remain friends with someone who isn't truthful about their sobriety. You came clean and you have good reason to be proud of that . . . as hard as it is to deal with.
I think I would tell your friend exactly what you've said here . . . . "I really like you a lot but I'm having some trouble dealing with the fact that your celebration isn't truthful. I hope you'll understand why I won't be able to join you for your celebration. I don't plan on letting that stand in the way of our friendship and I hope you won't either."