By Gyosone, the original source is gone. "Modern girls" were, essentially, flapper girls in Japan.

Source

Source - https://www.pixiv.net/en/artworks/42413978

Because they are the ones on top, looking down. (Taken 2018)

She thought they were cute, but she wouldn't admit it.

(2023)

Here’s the original artists by EU03.

Found on Tumblr:

https://www.tumblr.com/nightmarenetherworld/749975293035479040/couture-and-high-fashion-only-brings-to-mind-two

Source - https://www.pixiv.net/en/artworks/143262716

Source

Taken 2023. For some reason, Satsuki is one of the few Betty gets along with, so they have tea and discuss things.

Taking a break from looking after her ill sister, Satsuki plays a few notes on the koto with a little bird for company, its chirps acting like a metronome.