Why is Greta experiencing such a great amount of guilt after her mother's death in the novel, The Unsinkable Greta James?

Three months prior to the narrative present, Helen (Greta's mother) began suffering from bad headaches. Greta's father called her to report this news, but because Greta was performing in Berlin, Germany, she was reluctant to return home for something she was sure wouldn't last. Greta dismissed her father's concerns, and her mother died from an aneurysm shortly thereafter, plunging Greta into despair and remorse.