I can well relate to your feelings. Once you know the spouse has started a PA a painful new stage has been reached. Don't talk about it with your H. Just ignore her. Even ignore if he introduces your kids to her, as hard as it may sound. For your kids you will always be the best and only mother. Don't try to suppress the pain but don't nurture it either. Try to GAL as much as possible. Treat yourself as well as you can. All the best and take care.