Why won't she let me grow up?

My mom hasn't given me much freedom for the longest time. Im 14 and a freshman, she blocked half of the websites on my computer account she won't let me have my IPod and its been taken away for 4 months for having a fan instagram account and she constantly checks war websites I'm on. I'm not perfect but she sees every little thing i do. My sisters were never babied like this she never even asks what they are doing. She says she does this because "she can't trust me" but I'm not even allowed on Facebook. I'm not asking for much but i want some freedom at least just my IPod... Why won't she let me grow up? Is it because I'm the youngest and she doesn't want me to grow up? I try to show her that she can trust me but she sees everything and finds a way to make it seem bad... how do i get her to understand this?