I need advice?

I have never had a good relationship with my father and things have worsened since he got together with his fiance. They have broken up several times and have been engaged since 2005. They started planing their wedding and I was suppsed to be a bridesmaid. Since then things have gone down hill. I found out she was an alcoholic(through several horrifing experiences) and just overall a bad person. My dad ended things but they got back togehter and just now started the planning the wedding again.My father was forced to add her family into his groom partyand my older brother(from the good ex-wife) is his best man. Everyother member of the joining family(including her two daughters and grandkids) get to walk down the isle but my 10 year old brother is the babysitter to ring bearer and my sister and I were in charge of guestbook and don't even watch the wedding. To sum it up I am no longer in the wedding since I complained. I am against it but it hurts to not be included. Got any advice?