Final answer:
Vera tells Framton the story of her aunt's 'great tragedy' for her own amusement and to play a prank on him.
Step-by-step explanation:
Vera tells Framton the story of her aunt's 'great tragedy' because she enjoys creating drama and mischief. In the story 'The Open Window' by Saki, Vera takes advantage of Framton's gullibility and makes up the tragic story to entertain herself and play a prank on him.
Learn more about 'The Open Window' by Saki