Jam:
First off:
she told him something I told her in confidence.
Nothing you will ever say to the OW will have any effect. And Anything you do say will be used against you to destroy your Marriage. And you will never, ever have confidential communications with OW.
And second:
but she does not care for anyone but herself
That should be obvious!
And third:
She makes me sick to my stomach. I am just so angry and depressed I don't know what to do.
She isn't worth that.
Have you Exposed the Affair to the appropriate people, like OW Husband and other realtives to insure that she leaves your WH Alone?
Have you and your Husband prepared a "No Contact" letter as detailed in various places on this site?
That is really the only communication you ever need to do with OW.
Anything else feeds into OW desire to get YOUR WH back.
And to make her feel important.
Treat OW like an old grocery list, there it is cluttering up your purse, ball it up and throw it away....
Anything you need to know, you can get from your H. You need to be talking with him. This creates intimacy and closeness in your Marriage.
That will keep this OW and future OW away from you M.
And the letter you want to write? Go ahead and write it. Say whatever you are thinking/feeling/believing in that letter. You do not have to mail it. It might even make it easier for you to understand where you are, and over time, where you have come from.
You may even want to give the letter to your H. But if you say terrible things about the OW in there, He might be compelled to defend her. And you don't want that. Cuz that can get ugly. But, if it's how you feel? What you are thinking? Not LB/DJ/AO for WH? It can become a discussion starting point. And that's a good thing.
But OW?
She doesn't care how you feel. If she did, she wouldn't have tried to breakup your Marriage.
My BS was able to confront the OW and say various things on a couple of occassions soon after Dday. She wanted to say more, and really rude things too, but time passed. She talks with me. And we get a little closer each time.
.