Annoying sister

I really don’t know where to put this and I really need help. My sister keeps taking my stuff. And I realize that it’s normal, little sisters do this. But this isn’t normal. She’s wearing my used underwear and using my used razors, etc. I need ideas on ways to get back at her so she will learn her lesson and just stop. Ideas??

I’ve gotten a lock on my door but she still finds her way in. And I’ve involved my parents but they don’t seem to care. I’ve also tried to talk to her. This is literally my last resort. I need ideas