The Romantic.com

It wasn’t my idea, but sending a thank-you card (or letter) to your wife’s mom is a very respectful thing to do. The tone of it could be like this: “Thanks for my wife! Thanks for raising such a wonderful woman. I’m benefiting from all the time and love and tears you poured into her for so many years.”

This is an indirect way to love your wife since your mother-in-law gets some direct love from the note, but there’s a chance your wife may hear about it down the line.

It works.