Vera only asks Framton one direct question about his knowledge of the people in the area and one direct question about her aunt.
"Do you know many of the people round here?" asked the niece, when she judged that they had had sufficient silent communion.
The girl is fishing for information. There would be no point in asking Framton her other question if he said he did know some people "round here."
"Hardly a soul," said Framton. "My sister was staying here, at the rectory, you know, some four years ago, and she gave me letters of introduction to some of the people here."
What he means by "Hardly a soul" is that he has met a few people because of the letters of introduction. This is a good example of how a fiction writer will convey information to the reader through dialogue, which is usually more interesting than straight prose exposition. When Vera is satisfied that Framton knows nothing about the people in the area and that his sister probably doesn't know about anything that could have happened there in recent years, she asks her other question.
"Then you know practically nothing about my aunt?" pursued the self-possessed young lady.
"Only her name and address," admitted the caller.
The author has to establish that Framton is a perfect victim for the practical joke she intends to play. When she refers to the open window, it is not exactly a question.
"You may wonder why we keep that window wide open on an October afternoon," said the niece, indicating a large French window that opened on to a lawn.
This gives the girl her opportunity to tell her story about how the three hunters got sucked into a bog exactly three years ago and how her aunt, who had a mental breakdown, has been expecting them to return every evening since the tragedy occurred. Vera has to tell her story quickly because she has no idea when her aunt will put in an appearance.
Perhaps we should suspect that the girl has some ulterior motive for asking Framton her two direct questions when they first meet. But we do not realize, until after Framton flees in terror, that this innocent fifteen-year-old girl had been setting Framton up for a scare when the three hunters, supposedly dead for three years, return towards the open window in the gathering dusk and her giddy aunt says exactly what Vera knows she was going to say.
"Here they are at last!" she cried. "Just in time for tea, and don't they look as if they were muddy up to the eyes!"