Been there, done that. My MIL wore pale, pale, pale pink as her mother-of-the-groom dress. I wore ivory. Darn close in color, and she was well aware of the color of my dress. MIL threw my BIL and his wife another wedding due to distance to her family (Buffalo vs. Long Island), and this wedding really wasn't for BIL and his wife, it was for her to show off. Everyone knew it.
I've been married for 19 years, and about 6-7 years ago, DH finally "got it" and all my issues with his mother, and to a lesser extent his father.
The advice I will offer is the advice I got from a friend early on in our marriage who also had a difficult MIL: Let your husband handle her. It doesn't matter what I do or what I say, I'm always wrong or at fault. I've just come to accept that. DH realizes where I stand, and is on my side. It's his opinion that matters to me, not hers.
In the short term, she's already made the decisions for the party. It's obviously not about you and your fiance; it's about her and what she wants. Anyone at that party who knows you will know she created the party for her, not you and your fiance. Let her look like an idiot. People will catch on that it's about her because they'll see the wedding you and your fiance planned the next day.
This is another piece of advice I was given by a neighbor which I also use with my MIL: View her as entertainment. Yes, entertainment. Allow yourself to laugh at her antics instead of getting angry. As I said, the people who know you will know the party was not thrown with you in mind.
I know this is easier said than done, but don't allow her to aggravate you on your special days. DH and I said in retrospect that if you could plan a wedding, marriage was a breeze.
Best of luck! Congratulations on your marriage!
Michelle
