ok, I must admit I am surprised that a Pastor won't acknowledge an addiction and do something about it, and you said that if you can get your Pastor on board her parents will follow suit?
How woudl the pastor handle things if you told him she was just drinking heavily or gambling your family's life savings away?
See if he will read the article. He SHOULD be willing to read a damn article and educate himself. My feeling right now is he is ignorant about what an affair is or how to deal with them. That article is a very good start.
Hopefully he would be willing to read it if you printed it up for him.