I think my sister read my diary? VERY private stuff in there.?

Hi my name is Sophia and I am 13 years old. I have a diary with a spiral on the side that I put the pen in and I put in my desk. So, just today, I found my pen NOT in my spiral therefor I think my sister read my diary. She's been in my room a few times without permission to "get the music stand" and "put it back". And there was stuff in there about me kissing, my first real crush and boyfriend, my crush on a rock star, me having crushes on my teachers and that they are "hot" and in one case "sexy", and people at church. And also like temptations and problems that I've bend having. Stuff that my best friend or mom don't even know. And my plan was that to be secret for the rest of my life and she ruined it. She doesn't keep a diary so I can't really get her back. And I havnt really told her that I know yet and she's sleep now. I know my mom or dad didn't do it because they don't know that I have one. What should I do?? Thank you so very much!! And I forgot to add this, she's 11.