My sister leaves the toilet seat dirty

She showers 2 to 3 times a week. I've accepted this. I've read that it's completely fine, and when it comes to some people and their skin, it's necessary. My problem: the toilet seat is filthy *every* time she gets off of it. Yes, toilets need cleaning, but to have to clean it 4+ times a day and actually *scrub* because it's literal *grime* is insane. She also "can't see" the dirt even when it's pointed out so she refuses to clean it. I can't wait to move out and only have to clean up after myself 😩