My wife is petite (4'11") and always struggled to find clothes that fit her. She dresses conservatively because we're Muslim but she doesn't really like wearing the long gowns that many Muslim women wear, so she wears jeans and long sleeved shirts.
Anuway, she always struggled to find clothes that fit her well because she's small. Her uncle had to tailor a lot of her clothes growing up. A while back she found a fashion-as-a-service called Short Story, which markets itself for petite women; it basically sends her clothes every X-months and she tries them on and send back the ones she doesn't like or fit, tells her stylist why she is sending them back, and pays for the ones she keeps. Every time she keeps something from them she donates something from her wardrobe (net zero is the goal). And she looks great in them! They're fashionable (to the degree that my dev opinion on fashion matters), modest, and most importantly they fit her well.
Disclosure: I interviewed with Short Story last year as a consulting role but it didn't pan out.
If you've got the yen for travel, maybe visit an Asian country where she might be a "normal" size against the population.
I went to Vietnam and noticed the sizing difference for myself: suddenly I was oversized. I've also seen the opposite in other countries where sizes are much bigger and I'm on extra small sizings.
Vietnam is great for getting tailored clothing too - if you can avoid the worst of the tourist tailors.
Worth a try, if you can find a country that has a style she likes...
Before kids we traveled to Malaysia, Japan, Singapore. But since we are not really fashion-forward I don't think either of us cared to look at clothes there.
I did get a suit cheaply made and tailored in Malaysia back in college. One of the few pieces of clothing that still fits me perfectly now.