Sister stealing my underwear!!!

I am so tired of this and I've been dealing with it for years my 22-year-old sister still steals my underwear because she's too lazy to go out and buy her own and I don't know what to do and I don't know how to stop her but I'm so tired of coming home finding my underwear that were clean and in my drawers in her room on her floor dirty and used like it's fucking disgusting and I don't know what to do or how to stop it any advice?