Quite frankly, I have been feeling that nothing I do can snap her out of this. So I haven't put much stock in the idea that filing for divorce will make an impact on her. I would do it if I thought it would help me or help her come out of her fog but I honestly don't think it will.
My XWW was as far gone into her juvenile new-boyfriend, bullshit fantasy world as it gets. Her adulation and praise for her adultery partner was so far over-the-top that it was actually comical. The guy could walk on water according to her.
After D-day, I told her that there may be a chance of forgiveness and putting our family back together. I told her that there must be absolutely no contact whatsoever - that this man was now utterly dead to her and everything else for that matter. She agreed.
All that happened was that nothing happened. She just continued what she was doing. I'm sure she was texting with him within minutes of that conversation. She made sure of a decision to sabotage and destroy her very own family. She continued her "affair" - in her case, trading sex for flattery, for months after we had separated.
After about nine months after D-day, after nine months of her continuing her destructive toxic bullshit, after nine months of her threatening over and over that she was filing for divorce and me replying with "ok" - I filed for divorce.
After she was served I got the tearful calls asking if we could "fix this". I pressed on. When she lawyered-up, the first communication from her attorney to my attorney was that she wanted reconciliation. I pressed on. When we met at our first mediation, she cried the ENTIRE time, her attorney and the mediator came to me and said she really wants to reconcile. I met her privately during the mediation and she told me she never wanted a divorce and still loves me. I pressed on. From then on she was all about reconciliation. Literally minutes before the divorce was finalized she was still texting me that she did not want it to be final. It was finalized.
Now, after being divorced she still says she wants to reconcile, misses me, blah, blah, blah. Sometimes, the remnants of the guy I was before all this still thinks about grasping at glimpses of the time before all this shit and wants to to give it a shot. But, she really hasn't done the work and introspection needed to find out why in the fuck she would become a traitor to her family, her clan. Why she would drop every boundary she ever had for the sake of a gross and destructive delusion. Why she would give up almost half he time with her children for the sake of a total shitbag. I don't know and am caring less and less why and am only concerned about navigating my children through this despicable shitstorm and hope they come out ok.
My point is that the bullshit fantasy bubble was popped when I filed for, and aggressively pursued divorce. Like I said, she was as far gone as it gets. Her adultery was also supported and enabled by her dysfunctional and toxic friends, although her family was disgusted by her actions, behavior and friends. Her family was very supportive of me.
Your WW really hasn't experienced any significant consequence for her behavior. Keep in mind, this bullshit fantasy she is in is a big dopamine rush for her and she will keep that going for as long as possible until there is some real consequence that she cannot deny or delude herself away from.
Filing for divorce, having her served with the judge-signed Petition for Dissolution of Marriage is a VERY REAL matter. It sends strong messages to her - including the one that says you are not going to tolerate this shit from her any more. Also the one that says you deserve better than this Jerry Springer bullshit she has heaped upon you and your family.