In The Joy Luck Club by Amy Tan, how does An-mei's mother show motherly love towards An-mei?

In The Joy Luck Club, An-mei's mother's sacrifice displays maternal love.
An-mei's mother was dealt a terrible blow in being Wu-Tsing's fourth wife. When An-mei's mother comes back to her, all she has to do to show how much she loves her daughter is touch her "smooth-neck scar."  This shows An-mei that while her mother has been absent, she never stopped loving her. When she finds the wound that only a mother would know, it conveys love and devotion towards An-mei. 
An-mei's mother further displays love in the way she tries to give her daughter the strength she lacks.  An-mei's mother teaches An-mei the importance of strength and why sadness and suffering cannot be swallowed. This is another way that love is shown because she is teaching her daughter the lessons that life has so brutally taught to her.  When she has to return to Tientsin, An-mei's mother shows love towards her daughter by respecting her wishes:  "An-mei, I am not asking you.  But I am going to back to Tientsin now and you can follow me."  There is a respect for her daughter underscored with love.
An-mei does go with her mother and learns more about suffering, pain, and the way to combat them.  The classroom for such instruction is An-mei's mother's life as a fourth wife for Wu Tsing.  An-mei's mother teaches An-mei about the ways of men and marriage:  "You can see now, a fourth wife is less than a fifth wife. An-mei, you must not forget.  I was a first wife, yi yai, the wife of a scholar.  Your mother was not always Fourth Wife, Sz Tai!" When An-mei's mother breaks the necklace that Second Wife gave An-mei, it is one of the strongest examples of love that a mother can show a daughter:  "You do not believe me, so you must give me the necklace.  I will not let her buy you for such a cheap price."  An-mei realizes how much her mother truly loves her: "That necklace that had almost bought my heart and mind now had one bead of crushed glass."  An-mei's mother wants her to "recognize what is true" and avoid that which is false, a lesson forged out of love.
An-mei's mother loves her so much that she wants her to learn from her own example.  She wants her daughter to look at her own life as how not to live. When An-mei's mother dies, An-mei knows why.  While others believe she swallowed too much opium, An-mei knows the truth about her mother's death:  "She would rather kill her own weak spirit so she could give me a stronger one."  This shows the highest form of love that a parent can have for a child. It is the reason why An-mei is able to scream, raising her voice against an injustice.  An-mei is able to demand that her mother in death is respected more than she was in life.  She is able to right the wrongs done to her mother, and prove that the best love a parent can show to a child is teaching them the value of strength and honor.  An-mei's mother's sacrifices are a testament to both this lesson and the love she had for her daughter.