Final answer:
Amelia's secret that is revealed during her conflict with Zora is that she has African American heritage -- a fact that has major implications in her societal interactions.
Step-by-step explanation:
On the day of Zora and Amelia's fight, a significant secret about Amelia is revealed. The text implies that Amy, or Amelia, had been under the impression and had let others believe that she belonged to a well-off family with connections to the Kildares of Philadelphia.
However, the deepest secret that comes out is that Amy is colored, which in the context of the narrative and the time period, refers to her having African American heritage. This secret is significant as it directly impacts her relationship with others, including her acceptance by the society in which she circulates, particularly given the racial attitudes of the time.