There's nothing wrong, in my opinion, of writing letters. They can be very cathartic. Just don't hand them over or mail them.
Write as many as you need, keep a journal or blog (journal is better), and just write to your heart's content. It's amazing how helpful this is. I was NOT a believer in journaling until I started it this year. Now I can't get over how much it's helped me.
Sometimes we can say things in letters in the heat of a moment, that we wish we could take back....especially when you emerge from the other side when this is resolved!
That's why I recommend putting each letter in an envelope, and putting all those envelopes in one of those big manila folders, and just tuck it away.
You'll be happily surprised how good this will help you feel.
M.