In Out of the Dust, who does Billie Jo feel that she has let down?

In April of 1935, Billie Jo is asked to play the piano at the school's graduation. After the death of her mother and baby brother, Billie Jo has refused to practice on Ma's piano; the terrible scarring on her hands from the burns she incurred during the kerosene fire also make the act of playing the piano painful and difficult.

Despite this, Billie Jo accepts the invitation... and fails miserably. She sits on the bench and stares at the keys in front of the audience, unable to play because her "hands wouldn't work." As the long silence stretches out before them, the audience begins to whisper, Arley Wanderdale "lower[s] his head," and Miss Freeland begins to cry. Billie Jo feels that she has let down all those people who had expected her to play. "Too stubborn" to cry, Billie Jo gets up and walks off the stage in defeat.