Custine, I’m not sure. Portrayed as lonely and unsuccessful in writing. A half-man of letters. An outsider in Paris. Was praised by Balzac for writing on Spain, and produced a book about Russia for which he is predominantly remembered. –Notes from book- An unnamed character in Russian Ark.
Sylvia von Harden, I known even less of; had seen her portrait many times before I came across her name. According to her Wikipedia page, a journalist and poet, self-exiled to Britain in 1933 where she continued writing but without as much success. An homage is made in Cabaret. I took her photograph to the hairdressers.