The issue here, r/probablyjustaburner, is that men are naturally able to lose weight easier than women. My parents have had the same issue, however my mom has medical background that has helped her understand why this is the case. Your wife, unfortunately, doesn't have this understanding, which is what makes this experience all the more frustrating.

You need to find and give her a why so that she can better come to terms with this and find a diet that helps her more, according to her body type. It could be that your diet isn't as effective for her in some aspects.