Engagement Party. Who Pays?

I am marrying into a family where the parents are divorced. I am the groom. My bride`s dad has remarried and is worth a ton of money, however his new wife says that the proper ediquette is for the mother of the bride to pay for the engagement party. Is that the ediquette in a divorced parent situation? Who typically pays for what when the parents of the bride are divorced and both pointing fingers at the other?