As someone who recently purchased a high end chair, my only advice is go try them in person(!), and sit how you actually sit. Herman Miller Aeron for example is great for people who are either small or sit "correctly." If you fold your legs under yourself, it is super uncomfortable. My finalists were the Aeron, Embody, Steelcase Leap, and Gesture. The Leap and Gesture worked much better for my lazy ("natural") seatin…
There are 3 different Aeron sizes FYI, so if one is too small you might just need to try a different size.
I tried the B and C, both were uncomfortable for my normal seated position, my legs literally hit the underside/frame. For a smaller person, with shorter legs, they will likely have a better experience.