I think that not only should you send it, you should continue to write.

I used to do this with people, and later my therapist. Just write all of the attachment stuff pouring out my emotions related. At one point I asked her if she read all of them, and she said no lol.

Somehow, the letter writing was really for ME. It validated MY feelings. She really didn't need to read them.

The amazing thing? I just stopped writing. I didn't feel the need to write anymore, and I have never written a similar letter (not even CLOSE) since. (It has been 18 years)

So I would highly recommend that you write and send.