Having an issues

My sister is 12. When things don't go her way, she gets petty and upset. Today, she took one of my figurines and did something with it. I can't find it and it's one that doesn't fall (and if it does it's usually on my bed). I know the youngest didn't take it because he tells us that he did it once we notice. She on the other hand will lie until it's about forgotten and will slip up on it.

I did confront her and told her that I do not like that. That it's not nice not right for her to do that just because she's mad and didn't get her way. Bringing up the phrase "Treat people how you want to be treated". I'm genuinely very upset and disappointed because I trusted them to not touch my stuff or do me dirty like that since I don't do that to them either. They know I don't mind it as long as they ask or tell me and put it back. I make sure to do the same.

At the moment, I'm letting my anger settle and I'll retalk with her another time. What more can I do, especially to not escalate the situation?