Michael, I don't know about your specific area, but many good IC's work on a sliding fee scale in my home state to help ensure everyone gets mental health treatment.
If you are absolutely intent upon speaking to the OM's W, don't tell your W. She doesn't need to hear your plans. It would give her time to cook up a story with OM. Besides, it has nothing to do with her right now. You are one concerned and wronged adult speaking to another about two supposed adults acting like children.
As for what to say and how to say it, I don't have specific ideas here. But don't become confrontational. You are not at war with this woman. But she may not believe you, may not be willing to speak to you, or any number of other negative responses to your attempt.
undefeated 24 H 24 S's 4, 2, 1 M 5 yrs
"Most of the important things in the world have been accomplished by people who have kept on trying when there seemed to be no hope at all." ~Dale Carnegie