This is a good thread - about choices. I understand what you go through with your W, but it's just as 'off the wall' as my xh - once I came to understand what was truly going on.
First, I support you in whatever decision you make. I know you come from a place of love for your W and kids - that is a stance I trust.
Second, I think you need to remind yourself of the root here - this discernment is key and puts all standard DB advice into perspective. I think, when you're standing too close (as I do with my sitch) it's hard to do.
You have said that your W has a mental illness - not just MLC. Her more-than-usual-MLC bizarre actions have proved that. You tried to get her help. It has come close to harming your children. She cannot stick with the help. This is not about pointing fingers....rather, finding a bit more compassion for your W...and understanding your own choices.
So, if this is the case....understand this. She will hear your words, but she won't feel the regret and guilt you think she should. I tried this for too long. Honestly, they forget a lot of what they do. So, tell her for yourself, to vent to speak your mind. She's zapping back and forth each time I check your thread. That seems more of a chemical and mental health issue rather than an inability to commit or irresponsibility, or a bad life crisis - she went to a psychiatrist to get diagnosed.
There is a difference between a serious mental health issue and a life crisis/stage in life transition. There is a whole field in your profession dedicated to this. None of us are those professionals. We can give YOU advice on how to cope, survive and understanding, but not how to salvage a relationship from a person dealing with a serious issue. I want you to save your M, too. I also think your W needs more serious help in addition to tough love, finding God, doing a 180, or patience.
All of these things are good helpers for mental health issues - she needs prayers, patience, 180s with treatment or approaching it, and maybe even tough love. But, I have yet to hear a licensed psychiatrist say that is how they choose to exclusively treat patients with an imbalance. From what you write, it really seems that your W can't control herself. I saw that in my xh too.
Therapists are not there to make you understand anything. Therapists ARE there to give your W the help she needs to come out of this, or learning to live with a mental illness. I do believe that anyone who comes out of something serious, even like MLC, needs therapy to address core issues and perspectives. It does a world of good.
Again, I just want you to keep in perspective the root of your W's behavior. Core principles apply - but some things are very different.
I'm not saying to divorce or not. That is so personal. And, this perspective does not go against DB principles.