The woman on the left is Nancy Chih Ma; the woman on the right is her mother, Mrs. Chih-Teng Foo Chien. Arthur M. T. Cheng's arm is seen holding a broom on the far right.

Here is some additional biographical material provided by Juliana Cheng:
Arthur M.T. Cheng died in September 1989. Nancy Chih Ma, an author of about thirty Chinese cookbooks, was 104 years old in 2018. Her mother, Mrs. Chih-Teng Foo Chien, died in October 1998 at the age of 110 and is inurned at Santa Cruz Memorial Park. Nancy Chih Ma is the maternal aunt of Juliana Cheng.

More details from Juliana Cheng:
"Aunt Nancy Ma and Grandma Chih met the author of "The Good Earth," Pearl Buck, in the 1960's."
"Maternal grandmother was a Christian. Green card holder, she did not go through the Naturalization process to become an American Citizen. Son-in-law, the late Dr. Arthur M.T. Cheng, D.D.S. when in British Hong Kong, took in his mother-in-law so mother-Julia Cheng could reunite with her mother-Mrs. Chih-Teng Foo Chien after separations during 1937 Japanese attacked China, then 1949 Communist Chinese war with the Nationalist Chinese. Grandma Chih who lived to be 110 years of age, had more experience with war and turmoils in China. She was hiding in the cornfields with other women and children in her family in her pre-teens years, very likely that it was the "Boxers Rebellion" that she witnessed for some white soldiers with long gun killed her father when he begged the soldiers to spare his life and his family's hide in the cornfield nearby. Grandma could not understand how a little hole on the stomach of her father could kill him."