@Choux but what do people think she should be wearing instead?
As I said, I liked the monochrome chintz, but since you ask…
A few more slightly bigger or bolder prints and a few more dark backgrounds (I love bright florals on a black background). How about the occasional landscape/frieze print?
More separates. No need to tuck the tops or blouses in, so no problem to have a comfortable waist. Might increase the scope for prints? Printed skirt plus plain or textured top (I'm sure she'd do great white boho-ish blouses). Plain trousers and a printed top?
Some short or at least shorter sleeves (flappy or straight rather than puffed) and scooped/boatneck/slashneck necklines.
Fewer shirt dresses (just because I like very few shirtdress styles and none with long sleeves; I realise this isn't a widely shared antipathy amongst women of a certain age).
I actually quite like the safari suit look, but part of the visual appeal is that the wearer looks implausibly poised, cool and elegant for her tropical surroundings and, in the pictures we see, Sophie is usually getting involved with people and activities, so louche elegance wouldn't work. I think her figure may have thickened more than Anne's too, making tailored looks a bit harder to pull off.
I'm an advocate of wearing what makes you feel confident, so if that's endless long-sleeved shirt dresses for Sophie, that’s what she should wear. She has a much better eye for print than Kate, incidentally.