How Did I Miss this Book? "A Woman of Independent Means" by Elizabeth Forsythe Hailey
The novel is styled using the device of letters written by the book's heroine, Bess Steed, born about 1890; her letters span 1899-1968. The character is roughly contemporary with both my grandmothers. Like both of them, Bess knows certain hardships (even for the well off) of life a century ago: at 15, she is bedridden for a year with TB, later her life is upended by infectious diseases which are now more controlled and treatable. (One of my grandmothers lost her mother and baby sister to TB in 1900; the other lost three siblings by that same year when she was 10.)
Bess is irrepressible: she considers death the enemy, refusing to let anything stand in the way of her goals. She's a bit of a social climber in the country-club world she aspires, but endearing. You will chuckle at her social engineering antics.
The novel is a real page-turner, without chapters. The letters each make a natural divider of the action so you keep reading "just one more" all night.
The beginning reminded me of "Winesburg Ohio" with its small town flavor.
Later, I thought of William Styron's grim novel "Lie Down in Darkness", with the spoiled daughter Eleanor who gives her mother grief in parts of the book.