What announcement drives the main character to desperation in the story, The Lady Who Liked Clean Restrooms?

Fit and beautiful, Joy seems at age forty-two to have reached a level of satisfaction and serenity rare in the modern world. However, when her "strong, silent husband who wasn't so strong nor silent" demands a divorce to marry a younger woman, the rapid decline in her economic, social, and then psychic condition reveals the hollowness at the heart of everything that she has built her life on.