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Does she understand that being over-hygenic obviously has some negative impacts? Sure it is definitely better at preventing infection, but she's also reducing her exposure to good microbes which is what we rely on to not form allergies, asthma, and even some diseases.

This article summarises it well, but here's a topic-specific part.

But not all of our body has to be washed so stringently. Overall obsessive washing “disrupts the normal flora which keep you healthy by competing with harmful organisms”, says Ruebush. “Operating your immune system in an environment of sterility is like a sensory deprivation for the brain. Eventually, it goes insane, thus the increased amount of allergy and autoimmunity associated with persons who try too hard to avoid all exposure to anything in their environment,” she says.

Around the house, the solution for fighting the wrong kind of bacteria is not excessive cleaning, but timely cleaning.

You should at least being making your own stand for your own health and don't let her ways permanently compromise you down the track.