Hey @Jardin
This must be a really tough feeling to be managing and I'm sorry to hear you and you're sister don't have a good relationship. I think given you two don't have a great relationship it's understandable to be feeling uncomfortable, are there other things that she does out of spite that have made you concerned about your belongings?
Im sorry this is having such an impact on your life, if you're feeling like you are afraid to leave the house this must be very affecting, have you spoken to anyone else about this? Like someone else in your home?
I hope some other peeps are able to jump in here for some support and offer some ideas 
Hi @Jardin,
I am so sorry to hear about what you're dealing with, sibling relationships can be super complicated and tough to navigate, and it's totally understandable you're worried about your things! I was wondering, are your parents aware of the relationship dynamic/could you potentially have a facilitated discussion (with your parents) with your sister about how you're feeling/about your boundaries? Maybe setting some house rules could help?
Hi @Jardin! This sounds like a very difficult situation. If you and your sister have a bad relationship I can completely understand why you'd be nervous leaving her around your things, even if she hasn't stolen/destroyed anything in the past. My mind would be racing with the possible things she might do too if I were in your situation.
Like the others have mentioned, is there anyone in the house you could talk to about this who would be sympathetic? For example another sibling, parent etc - if they're understanding you could ask them to keep an eye on your room while you're out, or to have a chat to your sister about how this is making you feel (if you don't feel comfortable talking to her yourself.)
A perhaps more long term solution - could you buy a lock for your door? or some kind of device that allows you to monitor the activity in your room while you're out? if you're really worried she might tamper with your things, this probably would work the best practically.
Good luck with everything!
Thank you @Hannah-RO , @GioDes , @clarii3105 , @squiggly for your replies
Yes, I have spoken to my mum about how my sister makes me feel and she is aware of our bad relationship. Unfortunately, she tries to pretend everything is fine and gets angry at me whenever I bring it up. I also know that even if she promised that my sister will stay out of room, she could go back on her word and then lie about it when I got home (she has done similar things in the past).
I haven't even tried talking to my dad about it. I already know he would get extremely angry at me and I rather not get yelled at.
I really like your suggestions about getting about getting a lock for my door. In fact, I have wanted this for many years. I've asked mum before, but she always replies "don't be silly" or "why would you need a lock?"
I think the best I can do at the moment is try to hide everything that is precious to me. I'll ask my my mum again about a lock, but I doubt she'll say yes.
There'd be no harm in it! I hope your things will be safe whatever happens, feel free to let us know if there's any more developments.Thank you @squiggly and @clarii3105 , the lockbox idea is a good one.
To be honest, I really don't think my feelings are normal - or at least, they are too extreme to be normal. I mean I am actually terrified at the thought of my sister sleeping in my room and being around my things.
I hate that I feel this way. I hate that it is stopping me from leaving the house.
The thing that makes it worse is that my sister will probably be moving home for a couple months. I was so glad when she moved out (a year ago) but now she is coming back. I've had nightmares of her coming back, and now it's coming true. I'm just so scared. I don't know how I am going to avoid her when we are in the same house.
