Who is Mrs. Frola from Eleven Short Stories = Undici Novelle and what is their importance?

Mrs. Frola is the elderly mother-in-law of Mr. Ponza. Mrs. Frola believes that Mr. Ponza is married to her daughter but that he believes he is married to an entirely different woman. She may be deluded, but the reader is not told whether this is the case. She is devoted to her son-in-law, despite the fact that he will not let her see her daughter.