Whether you distance yourself, break it off completely, or try to salvage the friendship is up to you. You know the situation best.
In a perfect world, you would be able to have an afternoon together and curl up on the sofa each with a cup of tea and talk. You would each tell your story and be heard and not judged. You would each cry, and all would be well.
Only you know how much of that is possible. None? A tiny bit? Some?
Here’s my philosophy:
We are all hurting from the past. Some of us grow up in all ways and move past the hurts and move on with life. Some of us can’t do this for one reason or another. (The reasons are as numerous as there are people on the planet.) When we who have moved past our pain encounter those who can’t, all we can do is listen. Full stop. We cannot change the other. All we can do is support the growth of the other in whatever way the other decides to grow.
Now, in some cases, the other will choose a destructive way to grow. We then have a decision to make about how to “support” this. We can break off all communication and bluntly explain we will not tolerate the destruction. I think you can imagine the pain this will cause the other. We can give examples from our own story about how we grew and matured. These must be our own stories, and we must not use the word “you” even once when telling these stories. The other must be left alone to draw their own comparisons with their own story.
Some other ideas should the other choose destructive growth might be to simply disappear. In my experience this causes heartache for all parties. I would never feel peaceful disappearing. I need closure. You might decide to fully support the destructive choice and become a cheerleader for the endeavor. There’s also the idea of simply withholding your opinion of the choice and offering support when the pain from the destructive choice comes.
I got this somewhat long list of alternatives from a realization during a romantic partnership. The man I was seeing was not available when I wanted. He kept his own calendar, and I had to take him when he told me he was available. I was miserable, and then I had an epiphany. I could want more than he was giving and continue to be miserable, I could take what he was offering and enjoy that, or I could end it. I chose to accept what he offered and be happy. It later ended, but I had fun while it lasted.
I think what I’m trying to say is your friend is hurting, and she doesn’t know how to deal with the pain. She may not even be able to identify the pain. She’s probably harboring unresolved pain from childhood, the origins of which may be lost in time. It is not your place to help your friend get over this pain. It is not even your place to point out she may be in pain. Your job is to understand her pain and accept her anyway. All the while, loving and accepting yourself. Sometimes those are incompatible, and you must choose to nurture self before nurturing the other.
I am reminded of a quote from Ram Dass, “We are all just walking each other home.”
Can you continue to walk with your long-time friend, or do you need to take care of your own walk? Only you know.