Your mother-in-law was 100% correct!
While we are in galus, the operative term should be “hatzney’a leches”. It was for this reason that when Yosef’s brothers came to Mitzrayim, we learn that they each entered through different gates – i.e. because seeing 10 such chashuv, impressive looking men entering the country together would have caused a resentment and a sinah against the shivtai Kah.
I once heard a shiur from a well known Brooklyn rav where he spoke out against those who do not ACT (never mind dress, but ACT) with proper tzniyus. He used the example of a woman who will double park her luxury car in front of a grocery, run in to buy a container of milk, give the clerk a hundred dollar bill (because that’s all she has) while prominently displaying the expensive diamond bracelet on her wrist. That is NOT the way a Yid should act ANYWHERE, and kal v’chomer in galus. It defintely just fuels anti-Semitism.
Quite right, “at the end of the day, when we close our eyes for good” neither the fancy cars, nor the expensive jewelry will accompany us to the next world, BUT those kind of thoughtless, selfish acts, and in general the way we lived, WILL.