How does Selena discover that Carlos had actually seen Anita after she was turned away from the United States in the novel, The Wind Knows My Name?

When Selena talks to Carlos, he tells her that Marisol’s hair was the only thing that made her attractive and that she had cut it off. Selena realizes he is admitting he saw Marisol after she was rejected from the United States because Anita told Selena they did not cut their hair until right before they rode on top of the train.