I know you and I have discussed how we like having our kids to ourselves, nothing to worry about but fun with them. Try to focus on this now, think of your W as merely your kids ride to your house, or as a babysitter, someone you need to get updates about the kids from, but anything after that isn't needed. I wouldn't outright announce "Your blatant talk of OM makes me want to vomit, stop it at once". But I would get the info on the girls, and move on quickly.
And no more flirting for the time being. She doesn't deserve it right now.
