Help: Sister is making things difficult

So my best friend is planning my bachelorette party. She’s got everyone in a group chat and has done a great job so far getting everything organized. My sister, who is my matron of honor, will have just had her baby around the time of my party, which is why my best friend/bridesmaid stepped into to the planning role. Initially my sister counted herself out because of newborn duties. Now, after my best friend has found an Airbnb for 4 people and has pretty much finalized everything for the trip, my sister is saying she will come for one night. But it’s not just that- she is saying all the things she’s going to require: a full bed to herself, must room with me, needs space to pump, etc. my sister has always been a diva and a total buzzkill with all her requirements and comments. I feel like telling her it’s in her best interest not to come, but I don’t want to sound rude. How should I approach this?