Crushing HARD

I have a massive crush on my best friend and it’s been 8 months and it’s too much to keep in I want to tell her but I would be so miserable if she got weirded out. We talk about a lot of intimate things and I’m worried she’ll see me as a perv at this point. I was thinking a letter so I don’t pussy out? Or should I just keep it in? Every night I think about telling her and I’ve snapped out of it by morning.