Help needed with a girl

I'm really keen on this girl I am friends with, but am not sure what to do.

We've been friends for about 2 years, and we're both studying Year 12. She's an absolutely gorgeous girl with a great personality; couldn't be more perfect in my eyes. It's almost as if she's the girl I've been looking for my whole life. I've got an event coming up soon, and I'm thinking of telling her how I feel about her. The problem is I know she already has a boyfriend.

Would you tell her regardless? I feel I really have to let her know as I've kept it inside me for so long.

The fact that you admire her so much is as good a reason as any to kill yourself over. Girls hate pansy shmansy guys like you. Oh, "her eyes", stfu.