Abusive groom/unhappy bride?

I was asked to be in my friends wedding and was very excited to be a part of her special day. But recently, they have not been getting along and to even have a wedding was in question. The groom is abusive and is an alcoholic and she is extremely unhappy but it seems as if they are still going forward with the wedding. I've suggested couples counseling to my friend but they have done nothing to better themselves. I want to support my friend but I do not want any part of this wedding now. What do I do?