Sorry to be frank. I personally think that you should prepare for the worse first before you go and confront both your hubby and the woman.
However, as you have mentioned before that you have raised your concern to your hubby already but he insisted there is "nothing" between them. Honestly, if your hubby is a smart one, he should really know by now that it is not worthed for him to keep in touch with her and upset the family. Perhaps he is really enjoying the "relationship" right now and can't think of the consequence.