When W comes back home, treat her like a neighbor. You don't need to be too friendly or chatty with her.
As for MIL, shut it. Don't confide in her for blood is always thicker. Beside that, your W will feel betrayed that you broke your M's confidences with MIL. It's best to keep your mouth zipped when it comes your ILs.
You just don't know what W talks about with her family or friends. Ignore mindreading thoughts and stay on your path.
What did you do with the girls over the week? I hope it had some fun activities and just simply father-daughters bonding time.
