What would you do if your housemate asked you not to shower or flush the toilet after 10pm?

My housemate is sensitive to sounds and has asked us to manage our shower schedules around that. My housemate moved into my family's home, which I am living in due to complicated reasons (including a lot of medical bills). There are 6 of us, and she has asked us all to not shower after 10pm. My dad, who owns our house, comes home from work at the hospital at 12am or later sometimes. He tries to accommodate for her by taking 30 second showers with the water pressure on basically a tiny drizzle, but I feel bad for him that he can't even take a proper shower after being in the hospital. I sometimes work late until night to meet deadlines and it's hard for me to sleep when I go to bed dirty. This rule she's trying to impose on all of us feels extremely frustrating and inconvenient and we have tried to explain to her that we can try to accommodate her if we can but that our schedule does not always allow for that to work. She keeps asking us not to shower after 10pm and that if we do we should tell her so that she will sleep outside in a tent or van, which makes us all feel sort of guilty and uncomfortable.

The frustrating part is that she showers whenever she wants to, sometimes as late as 12:30am. She can be very loud as well, using her electric toothbrush in the hallways, opening and closing her door/the bathroom door half a dozen times within a short period of time before she goes to bed (I'm not sure why), and sometimes she talks and laughs very loudly at 12am or later. I basically told her that I can't guarantee that I can meet this request and sometimes I'll need to take care of my hygiene needs past 10pm.