I really hate this girl.
What is it about her that you hate?
Her voice is so high-pitched, I really can't stand it.
I'm sure her voice is very annoying to you, but it's something she can't help and you shouldn't hate her for that. Try to be more understanding of people's characteristics that they cannot change.
Don't you think it's rude to point out the obvious to me? I know I hate her and I have proof that she is annoying to everyone.
Are you sure that she is annoying to everyone?  I'd bet that there are other people who find her voice very attractive.