Oh I understand about other's feelings that you must consider. This is nothing to take lightly. Neither is what she's doing should be taken lightly.
You first mentioned what if S19 overheard her. Now you are saying her older D is coming and if she suspects anything she will talk straight to your WW. I get the impression you are kind of hoping someone else does it, to take some of the weight off you.
If this was an affair like in most of these cases, I would probably not even mention this, but have you considered a family intervention (you and her grown kids) if your W continues with this sex phone and the online activity? There have been a couple of times where there was a situation where something of that nature was needed in other stitches. I certainly won't push it if you don't feel comfortable about it, just wanted to plant that thought in you.
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!
