Actually, I wonder if La Vireville as a character split off from the M de Soucy of the story

It definitely seems possible! It's fun to compare both story and book, and think about how and why she developed the characters, especially ones as charismatic as La Vireville, and of course Raymonde <3

(On a somewhat related note: This is from 1910--it's interesting to see her love of the French revolution, and maybe some possible early ideas for this book? This Catoire she writes about reminds me a lot of La Vireville!)