Who is Mrs. Cooper and Mrs. Matthau from Answered Prayers: The Unfinished Novel and what is their importance?

In "La Côte Basque", a table near that of Lady Ina and the narrator is occupied by two married socialites, Mrs. Cooper and Mrs. Matthau. Their conversations make up almost as much of the content of "La Côte Basque" as does the gossip of Lady Ina, the portrayal of the two women perhaps suggesting that they are less lonely than Lady Ina, but equally as bored and equally as happy to be shredding the lives of their friends.