Sister keeps sneaking my laptop at night! IT IS DRIVING ME FRACKING INSANE!

Okay, so because I do my homework on my bed, my laptop is always set up a specific way. Well at night my sister has been taking it to her own bed, using it, not putting it back where it goes, and yelling at me because she is tired in the morning! she is getting to be such a little bitch! When I called her out for it this morning, she first tried telling me she didn’t do it, which I call bull because no one else would have done it. No one else DARES touch my computer. And yet she will sit there NOT PUT IT BACK and then yell at me for it. Second, she tried saying to me that I SAID SHE COULD. Can you believe that? Especially after her previous lie of “oh she didn’t do it in the first place”. When I called out that mistake, she sat there and called me a bitch and said she didn’t do it. I can’t put a password on it because my parents have completely drilled it into my head that if I do, I am in deep shit. I am getting sick of it! Please, what do I do? I am very close to telling my mom but don’t want the tattletale label. Oh, and after that, she sat their and said she was just going to ignore me.