My only advice is to make sure you are moving forward with your life. Don't stand still and wait. Doing that tells her you are solidly in place at her back up plan. Your only chance of saving your marriage is to get her to see you as high value. To be high value you cannot be her plan B. So you move forward with your life, improve in every way you possibly can, and let her feel like she is losing you. That is the only way to get her to question what she is doing.
When my wife wanted a divorce, she was dug in on that point as long as I was trying to hold on tight. When I let go and dropped the rope was when she started questioning what she was doing. As long as she feels like you are cemented on place as option B she will not question what she is doing.
