Long-time lurker, first time poster here.
My little sister recently got engaged, and is currently really focused on saving money for a house with her FI after their wedding. She decided that in order to do this, she was going to have a courthouse ceremony early next summer, followed by a big reception in my mom's backyard. All of this is fine and dandy, but in wedding discussions with her in the past few days, she brought up that "it will just be like a big party where everyone brings a dish". Now I know how incredibly rude this is to the guests, as does my mother, but my sister is extremely stubborn about this idea and is not listening to her arguments. We've tried the "your guests shouldn't be expected to bring anything" line and my mom offered to pay for catering and make some items herself, such as salads, stuffed shells, etc. She also offered to pay for the cake or cupcakes... whatever she wants. Little sister is not listening to a word of it, and turned down the offer of money from my mother.
Any suggestions for how to talk her out of this, or do you think it's a lost cause?