For years, my wealthy in-laws had a shameless little tradition: they’d invite friends or family out to the fanciest restaurants in town, order the most expensive dishes and bottles of wine, and then—like clockwork—suddenly “forget” their wallets or come up with some excuse to sneak away when the check arrived.

Every single time, someone else got stuck footing the bill. More often than not, that “someone” was my husband and me. So when they invited my mom to an extravagant birthday dinner while we were out of town, I gave her a heads-up. I warned her about their long-standing stunt and told her to be cautious. She just smiled calmly and said, “Don’t worry—I’ve got this.” And oh, did she ever. Just as I suspected, my in-laws pulled their usual disappearing act the moment the $1,500 check hit the table.

One by one, they made their excuses and slipped out, leaving my mom alone. But instead of panicking or reaching for her purse, she casually ordered a dessert and then asked to speak with the restaurant manager—who…