Please get individual counseling to work out your issues because the statement above shows that any advice given here is not getting through to you.
You don't HAVE to let her go. You HAVE to decide on whether you are willing to make the changes to restore your marriage or if you don't want to make the changes and let your marriage dissolve.
In either case, you are taking action for one or the other. But with what you've written above, it's clear you don't have the tools or desire even go down either path.
You are acting like it's a done deal, and there's nothing you can do.
THIS IS EXACTLY WHY YOUR WIFE IS LEAVING YOU.
YOU - the cheater - are acting you are the VICTIM and it's her fault.