How do I deal with my PA husband's over-controlling mother?

My husband is PassiveAggressive with Narcissistic tendencies. I have read and incorporated the book by Scott Wetzler, Ph.D., and, frankly, it saved my marriage. My husband is 49 yrs old and we are still having problems with his mother's controlling tactics. I just need some advice on how to deal with HER. It is/has come to the point of either she adhere to the guidelines that must be in place for any contact with her son, or none. My g-daughter and I are the ones who have to deal with the repercussions of his "episodes" caused by this over-controlling mother. Q: Do I step in and tell her what these guidelines are/will be....as my husband still cannot do this. I would only do so if he is at a point where he trusts me to not betray his confidences that he has entrusted with me, emotionally. We just had an episode where she sent him an age INAPPROPRIATE birthday card with a chastizing statement inside, which triggered the "guilt" psychological associations...he handled it well and he and I were able to discuss it openly together, but we will be faced with seeing her on New Year's Day. He hasn't seen her in over a year, his choice. Thanks so much for any suggestions.