How do Nella's actions isolate her from Giovanna in the novel, The Lying Life of Adults?

When Nella discovers her husband has been cheating on her for fifteen years, even before the birth of their daughter, Nella plunges into depression. Giovanna becomes disgusted by her mother's frailty and whimpering. She also hates that Nella continues to love Andrea so obviously, devoting all of her energy to worrying about his wellbeing. Giovanna has further disdain for Nella when she learns her mother has been sleeping with Mariano for years, despite her constant insistence otherwise.