Do you think I’m being sensitive like she said or is my opinion justified?

I’m 19, and I live with my sister because my mom is abusive and toxic. I live with my sister and her daughter, and her daughter and I share the same room. Her daughter will laugh for hours for no reason—really loud, like crazy. Even the simplest thing makes her laugh really loudly, and she keeps going even if you ask her to stop. She also leaves bowls and food in her bed. Recently, she even put a little piece of orange peel in my bed. When I told her about it, she got mad and denied doing it. She’s 11, and she claims that I’m just being sensitive and that I “can’t handle her behavior,” saying she’s just being silly.

Updates
9 mo
The laughing last for hour or more and she’ll start laughing like crazy and loud.
Updates
9 mo
I have a job and I don’t have enough money to move out yet
Do you think I’m being sensitive like she said or is my opinion justified?
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