Who is Mrs. Blandish/Madame Sisseretta Blandish/Mrs. Sari Blandine from Black No More and what is their importance?

Mrs. Blandish is Max's landlady. She disapproves when Max becomes white, and her hair-straightening shop, where she is known as Madame Sisseretta Blandish, goes out of business because of Black-No-More. Eventually, as Mrs. Sari Blandine, she patents Blandine's Egyptienne Stain when looking darker becomes socially-preferred and fashionable.