Basic DB technique says to do what ultimately will get you closer to your goal. If your goal is to push your W futher away, then call her right now and tell her she can't come.
I will refer to skills I am learning in my Dialectical Behavior Therapy class. You are thinking in 'emotional mind' regarding your thoughts to disinvite her. You need to be in 'wise mind'. That is to stay out of this. This is NOT your wedding. You are thinking emotionally and being selfish when you say its about you having a good time. What about your B and SIL's good time?
You have to realize that the thought of going to the wedding will weigh heavily on your W's mind as well. She will be thinking about a lot of different things while deciding whether she even wants to go. What if the wedding triggers something in her mind while there that jump starts moving towards a R? You will never know if it would create that opportunity or not if you don't let her come. You have a greater chance to create a positive outcome with her at the wedding vs. you not letting her. It will potentially create tremendous resentment. I think this can be a great DB opportunity. I would NOT recommend taking a date.
Don't get me wrong, FOBD, my gut instincts mirror exactly the way your initial post reads. F her. Ultimately, if you want to save your M, you need to do things that get you closer to that goal. That, and the fact that it is not your wedding screams to the fact that you are venturing into territory that you don't want to tread.
Any way you look at it, it is not going to be fun. Even if she is not there, you will be thinking about your W the whole time whether you want to or not. I went through the same thing after I split w/ my 1st W. It wasn't my brothers wedding, but my buddy who was like a brother to me. I couldn't help myself from crying as the ceremony was going on. As you can imagine, they were not tears of joy for the bride and groom. My XW didn't need to be there for me to be miserable.
You will need to monitor your alchohol intake either way, as well...
Remember....wise mind.
B.I.T.S.
M42 W38 D5D7 M8 Living as 'roomates' since 9-12-10 Moved out 1-7-11 FIL threatened to kill me 1-20-11