The only thing I'd change here is that, unfortunately, he didn't send multiple letters to Maximilien about her, but really only one, the one you quote from. It is, however, a very interesting story.
It took me days of research to find anything about her and, to begin with, her full name: Jeanne-Rosalie Guillodon de Tillet.
Ernest Hamel says she was the wife of "an academician named La Saudraye", most likely Charles-Joseph Lohier de la Saudraye.
Henriette Simon-Viennot, a 19th century woman historian, wrote an annex about her in her book about Marie-Antoinette.
"Madame de la Saudraye, veuve d'un riche libraire, était une charmante créole de vingt à vingt-cinq ans, qui vouait sa vie à la pratique de ces vertus difficiles qui n'obtinennent que le mépris des hommes. Elle avait quitté ses nonchalantes et chères habitudes des colonies, elle avait compromis sa fortune, sa réputation et répudié un cercle choisi dont elle était l’idole, pour opposer son ardente charité aux fureurs de Robespierre aîné par l’ascendant du jeune Augustin sur cette âme sanguinaire."
She goes off on a weird anecdote about how La Saudraye interceded on Simon-Viennot's father behalf to Augustin in order to save him from the guillotine -- a rather typical anecdote attributed to many women close to French Revolutionary men.
Charles Nodier tells the story of how she was refused at the Jacobins' Club in Besançon:
"Citoyens, les règlements de notre société interdisent l’entrée de son enceinte aux femmes. Je suis marié, je suis père et je n’ai jamais amené ni ma fille, ni ma femme. Robespierre, qui n’est ni marié, ni père, y a amené une femme. Je demande qu’elle sorte, ou que le procès-verbal constate au moins qu’un républicain a protesté contre l’aristocratie de Robespierre."
Some people, like Albert Mathiez, have argued against the accuracy of the anecdote (because Nodier is, well, always weird when he recounts things which he reportedly witnessed at 13-14 years old), but it's a verified fact that Augustin had trouble in Besançon with Bernard de Saintes, a fellow representative on mission, and the man who denounced her at the club was one of his partisans.
Also, interesting to note: créole doesn't necessarily mean mixed, but their reaction can still be somewhat racist-adjacent. Even if they were born of white European parents, people born in the colonies were seen as "exotic". It fits well with the Robespierre brothers' habit of mingling with people outside of Artois, much to Charlotte's and Guffroy's affront. At that time, "race" was provincial as well. (Or it could mean "class", as in "the Aristocratic race".)