Ok so, here's the thing, no matter what size a person wears, someone thinner than them could easily wear their clothes. I know that pedants will point out that the key word here is "fit," as though the fit is perfect, but you can always cinch and tuck clothes to make them fit, whereas it's much harder for a person of a larger size to fit in smaller clothes. My point is that the insult itself doesn't make sense because I person with a healthy body size could donate their clothes to someone who is thin due to lack of nutrition and it would fit them fine. If the wife was thinner than them, this would be a problem.