Your message to her should be simple and direct.
I had a few simple must haves to continue being married. First, immediate and permanent no contact with OM. Starting now. You compose an email which I'll review telling him this. Not a goodbye my love letter, either. One that tells him you know what you were doing was wrong and hurtful beyond compare to my husband and family.
Second, absolute and continued openness with cel, computer, email. She has broken trust, and openness will allow you to start rebuilding trust. She needs a new phone number and email address, too.
Third, the marriage as she knew it is over. Because of broken trust. She will not continue to be as free as before. Goodbye trips without you, for instance.
Fourth, no more lies. Or half truths.
It's her choice,,subject to these conditions
If she won't agree, you know where your marriage is.