I am going to break my cousin's phone.
Why are you going to do that?
She's an annoying bitch who always picks on me
Just because your cousin is annoying does not give you the right to break her phone, it is not okay to break your cousin's things. The right thing to do would be to talk about the issues you are having with your cousin.
But she keeps ruining my fucking life and causes me so much pain.
Well if you think you can't work things out have you tried avoiding her? If she is abusive as you claim you should not have to put up with her antics and should tell your parents.