My mum is checking everything i do and going through all my stuff,?

Create a "fake" diary that contains nothing but outlandish crazy stories. Say stuff like you are going out with a gangster that got you pregnant and that you are heavily into drugs. Say you got an abortion and that you have though about murdering someone. On the last page put "I told you to stay out of my stuff :)!" Make sure to make it sound believeable and let it drag on for a while so she thinks it really is true. This should create some good times lol!