Suizi's mother was a 'sent-down' Chinese citizen. From the 1950's - 1978, China had this (almost mandatory) scheme where intelligent, bourgeois city kids were sent to the poor areas of China to 'learn from the farmers' because having 'book sense' but neither 'common sense' nor life skills wasn't part of the plan to rebuild China. Families were expected to send one kid to the country, while other kids in the family could volunteer to go.Many of the girls who were 'sent-down' ended up married to (or pregnant by) uneducated rural men . With China's One Child Policy, girls like Suizi's mom were not going to divorce & go back to their urban homes, taking with them the child of an uneducated farmer because no one would marry them if they already had a child, and a daughter instead of a son.Culturally, Chinese people look down on divorced people, single moms, and the poor. Suizi's mom didn't want to ruin her chances of marrying someone who was her social and intellectual equal, so when her stint being 'sent-down' ended she chose to ditch her lazy, uneducated husband to go back to her hometown. She left Suizi because (as we know from these books) no man wants a used shoe woman who is dragging a kid. Suizi's mom didn't die, she left Suizi & her pig of a dad to return to her better life. In the villages, residents used to say the mother died if they pitied the kid and didn't want the kid to feel abandoned. In Suizi's father's house, they've taunted her by saying her mom is dead (meaning Suizi's mom may as well be dead as she never contacts Suizi). The stepsister just says Suizi was abandoned.In short, Suizi's mother left Suizi and her father behind to return to her educated city life.