Sisters Baby Shower

My sister is expecting in March and her mother in law is driving me crazy. My sister, mom and myself were planning on having the shower for my sister. We did contact the mother in law to make sure that the date was ok with her. Well ever since that things have gone down hill. The original date that was booked has been changed and now the location is too, due to mother in law. My sister also thinks she needs to know everything about the shower. Her and her mother in law came up with the idea to have a full course lunch for the shower instead of the basic finger sandwiches, veggies, and cake. My mom, other sister, and I cant afford all this and I`m the only one that has kids that I have to plan around. But for some reason all has broke loose. The mother to be is getting everything that she wants and we are the ones paying for it. I think is`s tacky. I ordered some things to give as gifts for game prizes and had to cancel that too. Mother to be doesnt want to play any dumb baby shower games. Did I mention that she has around 70-80 people invited to this shower? Mother to be had a "meeting" at her house the other day and never told me that the time changed from afternoon to 10am. ( the time that I would be at church). Mother in law made a statement that my sister and I are just the aunts and we shouldn`t even be involved. It should be the mothers that have the shower because they are the GRANDMOTHERS. I didnt know that grandmothers should be asking for gifts for their kids and neither should the mother to be!