Don't file anything - you will regret it. Or take any other "formal" step. There are others here who have filed for D, or moved out, or etc, etc, out of anger, etc. Now, they regret it. The WW drags it out all the time, etc.
Let her take the steps. Distance yourself yes, but don't take any "formal" steps.
Also, don't threaten to do so and don't push her to do it either. That will backfire. That was one of my many mistakes.
M:50 W:53 MR:20 D:21 S:17 S:11 BD-Sept 2015 Suspected PA Sept 2015-Confronted W & OM Dec 2015 Actually EA In house Sep:Jan/16-May 2016 W moved out:May 22 2016 OM-Intro Oct/17-On scene July/Aug 2017