You don’t have to push the divorce along (unless you want it), but you can’t really stop it either. Let her do the heavy lifting if she’s the one wanting it.
But don’t block or stand in her way. A LBS who tries to block/slow down/prevent divorce will usually help fuel an acrimonious disaster. You’re more likely to get more reasonable financial, custodial agreements if you don’t stand in her way.
Keep your head down and stick to DBing. Leave her steaming train wreck to her, and please trust us when we say it will be okay. Not today, nor tomorrow, not in a few months - but one day it will. I’d say the majority of the vets who have had their divorce finalised for 3+ years would probably describe it as a blessing. Mine certainly was, and I’m forever grateful she chose to have an affair because it was the start of a new, much better life for me and my children - it just that when you’re stuck in the middle of the grief an uncertainty, that can be hard to see.
Stay calm, stick with the DBing fundamentals, and let the cards fall where they may.