The statement that best explains how the excerpt reveals a moment of epiphany for Mrs. Pontellier is: She is going through a personal transformation.
In this passage, Mrs. Pontellier experiences a profound emotional awakening as she connects with the music in a way that stirs deep passions within her. The tumult of her feelings—described as swaying and lashing—suggests a significant internal change, indicating that she is moving towards a new understanding of herself and her emotions, which aligns with the theme of personal transformation in "The Awakening."