If she makes an argument about the gut microbiome/gut flora benefits, tell her that first of all, mainstream science doesn't even understand the first thing about the gut microbiome. We don't even really know universally what a 'healthy' gut microbiome looks like. Secondly, tell her that we have analyzed the Inuit before they were industrialized and they had excellent gut microbial diversity with a zero fiber diet. Generally, all they ate was seal blubber.