Let us remind ourselves that a metaphor is a piece of figurative language that compares one object to something else by asserting a direct comparison, without using the words "like" or "as." The most important metaphor in this story about the conflict between a mother and her daughter actually comes towards the end of the text, when Jing-Mei's mother gives the piano to her daughter in spite of the many disappointments she has caused her mother. Having asserted her "right" to "fall short of expectations," Jing-Mei sees this gift as a sign of acceptance of who she is and who she has become from a mother who has always appeared to want her to be more than she is. Note how the piano is described:
And after that, every time I saw it in my parents' living room, standign in front of the bay windows, it made me feel proud, as if it were a shiny trophy I had won back.
Now how the piano is described as a "shiny trophy." Jing-Mei obviously feels that she can use this metaphor to describe the piano this way because she believes she has won this trophy on her own terms and has not conformed to her mother's crippling expectations for her.