I don't know if you consider this an option, but clothing from the middle east, india, and southeast asia are all probably sized to fit your wife very well, they're usually "one size fits all" but people tend not to be as tall, so they are better length-wise for "petite" North Americans.

Things like this. Or a plainer this. And this. You can find them in all kinds of patterns, or in solid colors. Many are quite suited to western tastes.

Thai pants, thai wraps, kurtis, and things like that are easy to find on Amazon, but being in a large city, you might be able to find stores that sell this kind of clothing for the local hindu or buddhist population, and they probably have many totally western styles, with the same basic idea of covering yourself decently.