Overbearing?

My son is now 9 months old. His bedtime is between.6-8 based on his last nap time. We start our bedtime routine about 30 minutes before hand based on sleep cues from him. My mom lives 3 hours away and is coming to visit tomorrow. I told her naptimes are fluid but.he needs to go to bed on time and i need her to respect that. Shes staying at a hotel and its only for one day. Her response? Im being overbearing and need to let him have life experiences regardless of whether he turns into a cranky mess. I think its rude of anyone to come into someones house and willfully throw off an established routine. She thinks babies are fine without naps because we survived our childhood. So whats the verdict?