The best thing you can do, believe it or not, is to let her go. When a WAS comes to you and says they want a divorce, the best course of action is to say "Ok. I don't want a divorce, but I will not stand in your way."
Pressure and pursuit rarely works and usually just pushes them out the door even more quickly. Please read the post that job posted. It is pure gold in there. I would also seek out sandi's threads and writings. Her guidance during my sitch really helped me a lot.
DBing tactics are easy to learn. GAL. 180 and self-improvements. Detachment. Giving her time and space. They are extremely difficult to put into practice, remain consistent to, and not to make mistakes along the way. That is why job's post and all of the reading and links are so good because it will point you to real people on this forum that struggled with all of this before you.
You haven't said much about how you have handled this latest situation, though you told us a lot about what happened 3 years ago. How have you been dealing with her latest pronouncement?
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018