Why does my sister always snitch on me?

she always tells my parents everything.. even the small stuff and my parents of course yell at me. Even if dont do anything bad just small stuff like playing music out loud or saying something to her. she does so much to me and i never say anything but she feels the need to tell them every single detail no matter how stupid. She also makes comments on stuff that im insecure about right in front of my parents. If i forget to do something she tells them im irresponsible and immature when she knows my parents already yell at me because of stuff like that and she knows i get hurt by it. Im 17 and she's 15
Why does my sister always snitch on me?
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