Let's say you can see that your WW is chatting on Whatsapp. What would No More Mr Nice Guy do? Confront her as it happens? Reminds the boundry? Leaves home as the thought is unbearable? Get A Life and Detach?
If he has made a boundary regarding her chatting on Whatsapp, then he just needs to enforce it.
Did you make this a personal boundary? Is it for all chatting, or just certain people or when you are home, or what?
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!