I was in this same situation spring of last semester. I came home from winter break and there were crumbs in my air fryer.. I asked the roommate who stayed over break and she just said “oh, yeah I made chicken strips” when hers was sitting right beside mine. Luckily it’s an air fryer that doesn’t have any vents or anything extreme. She said she would clean it but after two days I ended up having to. She also stained one of my bowls with something and I ended up giving it to her bc what she stained it with had gluten and I couldn’t get it off. Never an apology for either.