Jing-mei sees an ordinary girl instead of a prodigy when she looks in the mirror.
Jing-mei’s mother wants her to be a prodigy, and this is something that she is completely on board with. After all, it is exciting for a young girl to think that she is special. However, after several failed attempts, Jing-mei seems to be getting nowhere. She starts to feel very discouraged. This is the point where she looks in the mirror and sees a failure.
Before going to bed that night I looked in the mirror above the bathroom sink, and I saw only my face staring back - and understood that it would always be this ordinary face - I began to cry. Such a sad, ugly girl!
Jing-mei hates herself when she looks in the mirror because she has not turned into the genius or prodigy that she thinks her mother wants to see. Fantasy has not lived up to reality. She has expected that she would just magically have some kind of talent and she would be transformed, without working toward it.
When Jing-mei tells her mother that she is not a genius, she gets a different reaction than she expected.
My mother slapped me. "Who ask you to be genius?" she shouted. "Only ask you be your best. For you sake. You think I want you to be genius? Hnnh! What for! Who ask you!"
Her mother wants her to understand that it is hard work, not effortless genius that she expects. Jing-mei has completely missed the point. She wants everything to come easily, without any work. Her mother is trying to teach her that when you put enough work into something, it will pay off. This is not the lesson Jing-mei is learning.
In fact, Jing-mei never really learns that lesson. The piano lessons backfire, because Jing-mei never really tries. When she returns to the piano as an adult, it is with sentimentality, because now she understands what her mother was trying to teach her.