The Joy Luck Club

The film begins with June's short narrative prologue about the swan feather in the opening credits and then her farewell surprise party in San Francisco for June's upcoming reunion with her long-lost twin sisters in China.
Among the guests are members of The Joy Luck Club, their daughters, other relatives, and friends. The characters narrate their journeys while they reflect upon their pasts.
The Joy Luck Club was formed by four women; Lindo Jong (Tsai Chin), Ying-Ying St. Clair (France Nuyen), An-Mei Hsu (Lisa Lu), and Suyuan Woo (Kieu Chinh), in San Francisco. The members have mainly played mahjong and told each other's stories over the years. They immigrated from China, remarried, and gave birth to children in America. Suyuan's daughter June (Ming-Na Wen) replaced her in the mahjong group when Suyuan died four months before the time the film is set. The mothers have high hopes for their daughters' success, but the daughters struggled through "anxiet[ies,] feelings of inadequacy and failure[s]." The mothers and daughters grow to know each other better and bond by the telling and learning of each mothers past to understand each other and overcoming their conflicts.Lindo and Waverly
In China, four-year-old Lindo (Ying Wu) is arranged, by her mother and the matchmaker, to be married to Huang Tai Tai's son when she grows up. When Lindo turns fifteen , her mother sends her to Huang Tai Tai, so Lindo marries Tai Tai's son, Tyan Hu, a pre-pubescent boy who has no interest in her. During four years of childless and loveless marriage, she is frequently abused by her frustrated mother-in-law, who believes Lindo's childlessness is her own fault. Lindo eavesdrops on the servant girl telling her lover that she is pregnant, so Lindo realizes her chance to leave the marriage without dishonor. Later, Lindo purportedly ruins her clothes and then claims that she had a nightmare in which Tyan Hu's ancestors threatened to punish her, Tyan Hu and the matchmaker. Then Lindo claims that the ancestors impregnated the servant girl with Tyan Hu's child. Tai Tai does not believe Lindo until Tai Tai quickly discovers the servant's pregnancy through inspection. Finally, Lindo claims that the matchmaker intentionally wrongly paired Lindo and Tyan Hu for more money. Tai Tai orders the matchmaker out of her family's life, allowing the servant girl to have her marriage. Lindo is able to escape the house and moves to Shanghai.Years later in America, Lindo has a new husband, a son, and a daughter named Waverly (Tamlyn Tomita). Between the ages of six and nine, Waverly has become a chess champion. Annoyed by Lindo using Waverly to "show off" at the streets, Waverly shouts at her mother and decides to quit chess. When she tries to play it again, Waverly loses one chess round, prompting her to retire from chess. Years later, she has a daughter Shoshana from her previous Chinese ex-husband and is going to marry a Caucasian fiancé, Rich (Christopher Rich), much to Lindo's chagrin. In order to make Lindo appreciate Rich, Waverly brings him to a family dinner. Rich fails to impress them especially by improperly using chopsticks and marinating the dish with a sauce, humiliating Waverly. A while later, at the hair salon, Lindo retells her moments with her own mother, and declares that she likes Rich very much, she then gives marital blessings to Waverly and Rich, prompting her and Waverly to reconcile with each other. At June's farewell party, Rich almost successfully uses a chopstick but accidentally drops a piece, impressing Lindo.Ying-Ying and Lena
In China, Ying-Ying St. Clair was happily married to Lin-Xiao (Russell Wong) with a baby boy in China until Lin-Xiao abused her and abandoned her for an opera singer. Lin-Xaio is seen at his happiest when he is cruel to Ying-Ying, especially in bringing his Opera Singer home to engage in sex in front of his wife, calling both women not better than whores. Overcome by her depression, Ying-Ying drowns her baby son in the bathtub. Years after she immigrated to America, she struggled with her traumatic past, frightening her new family, including her daughter Lena (Lauren Tom). After Ying-Ying finally resolved her years of trauma, Lena shows Ying-Ying around her new apartment with her Asian American husband Harold (Michael Paul Chan), who is also Lena's boss. Lena is uncomfortable with her financial arrangements with Harold. Even though Harold makes nearly seven times Lena does in wages, he insists that they split the costs of their life evenly with a list of things that they share, making their home life contentious. Lena feels her husband has no respect for her. Seeing that Lena is unhappy with her marriage, Ying-Ying knocks over a table in the bedroom and causes the vase on it to fall and break. Lena goes to her mother, and admits her unhappiness. Ying-Ying replies that Lena should leave and not come back until he gives her what she wants. At the farewell party, Lena is shown to have another fiancé and announces her plans to go to Lake Tahoe with him.An-Mei and Rose
Nine-year-old An-Mei Hsu (Yi Ding) is reunited with her long-lost mother (Vivian Wu), who was disowned by her family for her "dalliance" with a wealthy middle-aged man Wu-Tsing shortly after her husband's death, and who arrives to see her dying mother (Lucille Soong). In order to not lose her again, An-Mei moves out with her mother to Wu-Tsing's house against her relatives' wishes for her to remain with them. She finds that Wu-Tsing has another three wives, making An-Mei's mother the Fourth Wife(the equivalent to a Concubine). Later, she learns that the Second Wife tricked An-Mei's mother into being raped and impregnated by Wu-Tsing. When the relatives did not believe An-Mei's mother and kicked her out, she reluctantly became Wu-Tsing's Fourth Wife as she had nowhere else to turn. After she gave birth to a boy, the Second Wife took him away from her and claimed him as her own. After An-Mei discovers the past, her mother ultimately commits suicide by eating "sticky rice balls" laced with opium, choosing the day of her death carefully to threaten Wu-Tsing with the vengeance of her angry ghost. Afraid of this curse, Wu-Tsing vows to raise An-Mei and her half-brother with great care. When the Second Wife tries to stop Wu-Tsing from letting this happen, An-Mei suddenly destroys the remains of the faux pearl necklace, indicating that An-Mei is aware of the Second Wife's cruelty and manipulation. Second Wife backs down, realizing the trouble she caused for An-Mei's mother and that she lost control of the house.
Years later in America, An-Mei's daughter Rose (Rosalind Chao) has been dating her boyfriend Ted Jordan (Andrew McCarthy) since college. When he confronts his aristocratic mother (Diane Baker) for insulting Rose mainly due to her race, Rose is impressed and agreed to marry him. During the marriage however, Rose and Ted become distant from each other, and despite their problems Rose remains submissive to Ted. They have a daughter but this does not resolve their marital problems. To make matters worse, Ted cheats on her with another woman. An-Mei compares Rose to her own late mother. To avoid having the same fate, Rose stands up to Ted, reclaiming her strength, by telling him to leave the house and not take a daughter away from her. This compels Ted to take her seriously and not continue taking her for granted. At June's farewell party, Rose shares with Ted a slice of cake and feeds him frosting as they share a loving moment.Suyuan and June
The setting is early World War II, when the Japanese invaded China, Suyuan Woo escaped the invasion with her twin baby daughters and all her posessions, seeking refuge in the northern Chinese territories where the Japanese have yet to make a stronghold. When Suyuan became ill with dysentery during her quest for refuge, her cart breaks down, causing the babies to fall. Suyuan abandons all her possessions to carry the babies to refuge. Near death, Suyuan was unable to carry the babies herself, realizing that no one will help her and abandoned them at the base of a large tree, (knowing that someone will take the babies) along with, all of her jewelry, including a photo of herself and a note that promises more money if the babies are delivered ot their father in the North. Suyuan was taken in by a passerby, and survived, but was haunted by the loss of her daughters and never knew what happened to them.
After she remarried in America, Suyuan has high hopes for her new daughter June, but June constantly fails to meet her expectations out of a lack of interest. She performs badly during a piano recital at age nine, and when Suyuan pushes her to continue training to be a concert pianist, June refuses, saying that she wishes herself dead like Suyuan's other daughters. At a dinner party a year before Suyuan's passing, Waverly Jong, June's long-time rival whom she is doing advertising copywrite freelancing for, turns down her business ideas as not meeting the needs of her company, and Suyuan implies Waverly has more style than June. The following day, June berates Suyuan for her remarks and admits she could never live up to her high expectations. June says that Suyuan is disappointed in her because June dropped out of college, is never married, and does not have a successful career. However, Suyuan gives her a jade necklace and explains that she meant June has a far kinder heart than Waverly and has style that she was born with and that cannot be taught.Last Easter before the farewell party, June received the news from the Club that the long-lost twins were alive. When June could not understand the twins' letter written in Chinese, Lindo purportedly mistranslated the letter to make June believe that the twins knew about Suyuan's death and their long-lost half-sister June. When the farewell party ends, Lindo confesses that she wrote letters to the twins and then signed Suyuan's name. June begs Lindo to tell them the truth, but Lindo will not interfere further because the twin sisters still believe Suyuan is alive and that June must tell them herself. When she arrives in China to meet her sisters, June tells them the truth about Suyuan, and embraces them. In finally accepting her Chinese culture, June is able to make peace with her deceased mother.

Question: Why was An-Mei's mother disowned by her family?
Answer: Dalliance