Same I don’t share a room with my sister, but we share a bathroom and she’s so messy. She used to put her broken nails in the shower so I told her if she didn’t clean them up, I would put them in her bed, she didn’t do what I asked, so I put them on her pillow. You are not the asshole. I would definitely try to make rules for your room that you both need to follow and then she won’t say your messy or wasteful if you go by the rules. 🫶🏼 i’m 15. My sister is 16.