Toxic sister

My sister is a really horrible person. She is fake to all her friends. She talks so bad of them to me and anyone else out of school but she hangs out with them every single day. She criticizes girls in her school for being confident in themselves and when my mum asks her to do exactly that she makes excuses and walks away crying.
She always has a go at me. She is 11 years old and her mouth is so big it disgusts me. She is so horrible to my mum as well and when she gets told off she doesn't care. Anytime she says something new, she wants it. I come from a well off family, so it is never a problem for her to buy anything new and just cries about it. She has so many expensive things, for doing nothing.
She gets let off with everything. Me and my brother back her up sometimes when she gets into petty arguments yet when we ask her for anything she throws it back at us.
She is abusive to my little brother. Not physically but mentally always saying things so he feels stupid. My brother is in year 5 and it sticks with him. Whatever she has said or done, he remembers months later and it is disgusting.
She is so sly as well. Back when I had a phone- which I no longer do because of her lying to my mum and now she has taken it off me- she used to read very message and send every picture I have taken to her email so she can blackmail me with it. I know I am older but this girl is next level for real.
I asked my mum to pick me to school, because I have to take the longer way round and I am a bit scared on my own after I had been harassed and sexually assaulted. She started crying because she was scared to cross one road to get to school. So, every morning my mum drops her and picks her up. Because of her being so childish, my mum can never pick me up and I have to walk.
She disgusts me a lot and I am so embarrassed to know her. Because of her literally I am scared to be in my own house as sad as that sounds.
None of my cousins want to be associated with her because whenever they come round she talks low of them in their faces or tells my mum lies about them till the point where my dad has to call up my uncles and ask what actually happened.
She keeps an eye on me all the time. At school. Whenever I am studying or speaking to a friend on my laptop she walks in and goes show me your laptop now. And off course I refuse she has no right! And then when I do show her, she goes show me you history like wtf?
She goes on my younger brothers Roblox account and bullies his friends and then when there mums come to my mum my brother gets told off, till after my sister is upstairs I have to explain to my mum.
She is disgusting and no she has no trauma no nothing to be like this. She has always been this way the day she was born.
She causes arguments between my parents to the point my mum asked for a divorce. Luckily, that got sorted otherwise I would have for real sent this girl to live in a bin.
I have tried being nice to her, I have tried ignoring her but just never works. I hate my life to be honest. I have nearly done reckless things just because of her.
And I know I am being pathetic, I am 4 years older than her but there is nothing I can do anymore. She scares me to death.

Thank you for reading! I just need some advice on what to do because neither of us are leaving this house any time soon and I really cannot take it anymore. If anyone can help it would mean the absolute world to me!
xx

im so sorry to hear that your sister treats you and your family this way. could there be any reason she acts like that? you dont sound pathetic at all.

There is no reason at all. She hasn't had any trauma, her life has been perfect since the day she was born.
Thank you for reading and replying! x

^ could something have happened before that you dont know about?

There could be a few things that could make her be like this
1) maybe something happened to her that only she knows and she’s acting this way to hide the fact that something happened
2) there could possibly be a problem at school, I mean it’s quite strange for an 11 year old to want to have their parents help them cross the road
3)maybe she just likes the attention she gets when she acts this way
It is weird that she constantly asks what you’re doing and to look at your search history but there could be something up, try to have a conversation with her. I’m really sorry you and your family is going through this but I’m sure one day she’ll grow up. Also talk to your little brother, no one should have to go through mental abuse

Not from what I know off. She has been like this since she was younger, it's just getting worse & worse.

tbh she sounds like a narcassist or has narcassistic personality traits. i would get her a therapist tbh.

I asked my mum to pick me to school, because I have to take the longer way round and I am a bit scared on my own after I had been harassed and sexually assaulted.

Has this assault been reported to the Police?

No! This was when I was in year 7 & I am in year 10 now , & I was to scared to tell anyone. He's been reported though, because he did the same to my friend.

Was he prosecuted?

Yes he was! Back in 2017.

But you didn't tell the Police what had happened to you?

No! This was when I was in year 7 & I am in year 10 now , & I was to scared to tell anyone. He's been reported though, because he did the same to my friend.

No, I didn't. I only told my parents a few months back.

And was he convicted and sentenced?