I will leave others give their views about approaching OW. I think you need to take your focus off of her. In reality she is only an issue because W let's it be an issue. You have asked her to NC OW. She has refused. Now what?. This in itself does not mean she is still wayward or that something is going on. It does show a lack of full commitment to your R as she is not willing to do so.
In the end you cannot force her. Shouting will not help. Instead I think that you need to go back to basics. FOCUS on YOU. Back the hell off W, pull right back, but not cold. Get on with your life. GAL.
Yes there is a chance/risk that the A restarts. Again out of your control. Have your boundaries in place and know what you will do if crossed. Knowing this will help not to react with anger.
You are in a tough position and it sukcs to be back there. I am sorry the path hasn't been smoother.
Reread your signature and live it. Best wishes
R 25 years M 14 years S11 & S13 Working on it alone since Oct 2014 M in trouble a lot earlier (~2 years) Feb 2016. 1st R chat in a yr. Next R chat Aug'17 Still together