This sucks. Positive thoughts your way.

From a family systems perspective, there are a lot of triangles happening here, and I would suggest that as painful as it might be, the only way this will ever get solved is through direct and unambiguous positioning on your part. You cannot control her behavior - you can only control yours.

You mom, as wonderful a person as she might be (and from what you say, I'm sure she is a wonderful person), has made a choice, and because of your relationship with her, her choice is one that also forces a choice upon you. That is, do you choose to maintain a relationship that is trying to corrode the relationship you have with your wife?

Another triangle here includes your dad, who understands what is going on.

It's easy to give advice, but I think - if I wanted to choose my marriage (and I would) - I would do the following:

1) Call dad & tell him that you love him & want to maintain relationship with him, but that you're going to have to cut off your relationship with your mother. Figure out a way that you can communicate without your mom.

2) Call your mother with your wife present - that way, everyone gets direct communication with no manipulation through triangling later on. I would say something like "Mom, I love you very much. You have decided that I must make a choice between a healthy relationship with my wife, who I love and to whom I have promised myself forever, and an unhealthy relationship with you, whom I love and respect deeply. I hate to make this choice, but since you have demanded that I do so, I will. Until you have regained a sense of balance and health, I will not accept phone calls, emails, invitations or any other sort of communication from you. I do not have any requirement for how this relationship might reform, because I don't know what those might be, and I don't want to put a set of hoops in front of you. I'm maintaining my relationship with dad, and if you try to use that relationship to hurt me, you will be damaging that relationship as well. My deepest hope is that someday all of us might be reconciled, and I am brokenhearted that you have decided to force me into this choice. I love you." <hang up.>

3) Block her phone and email and whatever else communication might get to you. Your choice if you want to read snail mail.

4) Mourn your loss.

Maybe there is a less drastic way to do this, but I don't know how I would do anything other than this is my marriage was indeed the most important relationship in my life. I hope you're smarter than me.

Peace.