The policy of e-notes is to answer only one question per posting. You should submit separate questions for Vera's and Framton's dialogue. I have chosen to analyze the dialogue of Mrs. Sappleton because it seems especially revealing, and I have edited your question accordingly.
Mrs. Sappleton seems like a woman who has spent her whole adult life being nothing but a hostess and a household ornament. She has a line of mindless chatter which she uses as all-purpose conversational fodder. She doesn't really listen to other people, and other people probably rarely listen to her. In other words, she can talk without really thinking and listen without really hearing. She is quite different from her young niece Vera, who is intelligent and inquisitive, but who might become another Mrs. Sappleton as she grew older, married some country gentleman who "hunts in dreams," to quote Tennyson, had no intellectual stimulation, and heard nothing but talk about hunting.
A good example of Mrs. Sappleton's dialogue is the following:
"I hope you don't mind the open window," said Mrs. Sappleton briskly; "my husband and brothers will be home directly from shooting, and they always come in this way. They've been out for snipe in the marshes to-day, so they'll make a fine mess over my poor carpets."
She rattled on cheerfully about the shooting and the scarcity of birds, and the prospects for duck in the winter....He was conscious that his hostess was giving him only a fragment of her attention, and her eyes were constantly straying past him to the open window and the lawn beyond.
Mrs. Sappleton is isolated and virtually imprisoned in this country home where the only conversation she ever hears is about what interests the three all-important males in her life. She is not really interested in hunting, and she rarely goes outdoors. She has become brainwashed by her immersion in the male talk about snipe and ducks, guns and dogs. Obviously she lives for her husband and her two brothers. If she doesn't talk to them about their subject of interest, she wouldn't be able to talk at all. She has become conditioned to think she is interested in shooting birds and knows something about the subject.
Vera has heard her aunt's dialogue so often that she knows almost precisely what she is going to say when she starts talking to their guest Framton Nuttel. That is why the mischievous girl is able to concoct her ghost story and actually to bring off a little theatrical production. She knows, also, what the three men are going to say when they return home in their muddy clothes with their bloody trophies. She knows that Ronnie will start singing, "I said, Bertie, why do your bound?" It is only because Vera has heard Mrs. Sappleton's mindless dialogue and seen the hunters returning so many times that she is able to create a story which will produce a predictable effect. The nervous Mr. Nuttel will go running out of the house and down the country road, afraid to look behind him because he would expect to see three ghosts chasing him with guns. At least Vera will introduce a little excitement and amusement into the monotonous existence at the Sappletons' country manor.
The clueless Mrs. Sappleton is characteristically bewildered and confused by Framton's flight.
"A most extraordinary man, a Mr. Nuttel," said Mrs. Sappleton; "could only talk about his diseases, and dashed off without a word of good-bye or apology when you arrived. One would think he had seen a ghost."