Final answer:
Details that best characterize the woman as a lonely person include her feeling of a growing gulf between herself and her partner, her inability to express an undefinable uneasiness, and statements of her experiencing loneliness in New York.
Step-by-step explanation:
To determine the detail that best characterizes the woman in the excerpt as a lonely person, one must look for textual evidence that reflects her isolation or emotional distance from others. In the given passages, three specific details stand out: "If Charles had but wished it, if he had guessed it, if his look had but once met her thought, it seemed to her that a sudden plenty would have gone out from her heart, as the fruit falls from a tree when shaken by a hand.
But as the familiarity of their life became deeper, the greater became the gulf that separated her from him." "Perhaps she would have liked to confide all these things to someone. But how tell an undefinable uneasiness, variable as the clouds, unstable as the winds? Words failed her—the opportunity, the courage."
"She was lonely in New York. Perhaps it was the first time in her life that she had felt so. The days dragged on emptily." These details indicate the character's emotional distance, desire for connection, and the pervasive feeling of loneliness that she experiences in her life.