M.P.
C., you are her best friend. Wanting her to live a better life for herself and her son is a part of being a best friend. But it sounds now like you need to also be your own best friend. Your friend's situation has become damaging to your peace of mind. You need to take care of yourself.
That doesn't mean that you abandon your friend. It means that you put some boundaries on the relationship. All good relationships have boundaries. What you're wanting your friend to do is put down some boundaries with her husband and enforce them. One boundary that I suggest for you is that you tell her that you cannot listen to her anymore because it is negatively affecting you and thus your family. Tell her that you love her and that as she knows you're very concerned for her and her son but when she's not willing to do anything herself to make it better the listening is not helping anyone, including her. I believe that just as in the case of an alcoholic whose friends provide beer for him by having it in the house, perhaps you you are enabling her to stay in this relationship by listening to the same stuff over and over which allows her to focus on what is happening and not moving on to finding a solution. She is also getting other "pay offs" for staying in the relationship that are probably not recognized by her or you. Having the relationship she has with you is a pay off in some way for both of you. Otherwise one or the both of you would change it.
I'm not saying that if you stopped listening she would move on. I just know from the hisory that you've told us that what is happening now is not working. And there are reasons that you are both stuck focusing on something that makes you both unhappy.
One of the most difficult lessons that I've learned is that I cannot fix anyone else. Each one of us can only change ourselves. Sure, we can be a supporting friend and offer suggestions but only when they are asked for and only when doing so does not harm ourselves and our other relationships. Meaning we can't tell our friend what to do and then take on the responsibility of being sure that she does it. When we take on responsibility for the other person we do become anxious/depressed because we do love them but we do not have any power to help them change unless they have asked us to help. A feeling of lack of power is one of the reasons that we do get depressed.
And for me I learned that I continued to try to help someone because I believed that was my responsibility. The pay off for me was the sense that I was being their friend by listening and trying to help them find a solution when in the end they did not want a solution. They only wanted me to listen. For years I couldn't do that because of my own strong sense of responsibility to make life right, to protect children, to make friends happy, etc. But in most situations I have no authority or power to do any of that when the other person isn't also working on doing that. We have authority over our own lives and those of our children. We may have influence with the adults in our lives but we only have that when the other person gives us that ability.
I keep writing because I'm not sure if I've adequately explained myself. And the subject is one with which I've struggled all my life. I've invested much of my own emotions and time with friends that I believed needed help. And in reality they did. The relationship sometimes started with them asking me for help. This one did. He was an alcoholic who was ruining his relationship with his children and cried on my shoulder often about how his life wasn't going the way he wanted it to. I didn't keep beer in the house but I did let him cry on my shoulder anytime he wanted to do so. But finally I got tired of always being around someone who was upset about his life but not willing to do anything to make it better but at the same time very upset that he wasn't listening and holding on to the friendship because it did make me feel that I was doing the right thing. I increased the amount and intensity of my advice, thinking he just hadn't heard and I could make him hear me, but he wondered off to find someone else who was more willing to just listen without trying to change him. Or more importantly not trying to make him feel responsible for his own life.
In this instance, he has continued to go from person to person trying to find someone who will accept him as he is, a chronic drunk and complainer. Last I heard he was going thru his 3rd divorce and still has no clue as to how he can help to make himself happy.
Years later I learned to not take on the savior role and saved myself and the other person, who wanted to be saved, a whole lot of pain. I could not save them and they could not be saved by anyone except themselves.
You have a longtime friendship that has become so painful that you're somewhat relieved to have moved away. Your situation is different from mine in many ways. But the premise is the same. You cannot do anything to make her protect herself and her son. All that you can do is protect yourself. If you not being willing to listen over and over to her painful life which she's not willing to change causes her to leave
the friendship it will be very sad. But you will not have been the one to end the friendship which will make you even more sad. If you end it you've taken responsibility for ending it. If you set boundaries you have taken on responsibility for taking care of yourself.
And if you stop listening to the complaints and stop telling her what she should do she may be able to see for herself what she needs to do and you'll still be there to support her when she does leave this abusive relationship. I think, in addition to taking on responsibilty that doesn't belong to us, we also keep trying and get stuck in a rut that prevents us from seeing any other alternative. If what you're doing is not working for you then try something else. Ending the friendship seems like going from one extreme to the other. I'd try something else in between first, especially since you've been friends for so long. But I'd remember that my own well being comes first. We can give too much of ourselves away and not have enough left to do what needs to be done for ourselves and our family.
I wish you the best. This is a difficult situation to work out. I think that whatever you do you'll find that you'll have learned alot about yourself and can be glad for your own personal growth.