Fanny Crowne was the close friend of Lenina. The phenomenon of the same surnames was frequent in their society and could be explained simply. Only ten thousand surnames were allowed to be in use in their dystopian world. Fanny was a conventionalist. She was the one, who pushed Lenina to have more partners. What is more, she was the one who pushed her to flirt with John; however, he turned her away. Fanny convinced Lenina that it was not good to concentrate on one person for too long. She was rather materialistic. The author makes Fanny a fictional character so that Lenina had somebody to talk with and share her thoughts with somebody.
Fanny Crowne in the Essays