How does the niece use the open window, the spaniel, the white coat and the bog to create a forge story?

Vera uses everything she has at her disposal to create a realistic tale. She is polite, congenial, and a good hostess, seemingly drawing Nuttel into a harmless discussion until her aunt appears to greet him. When Vera announces that her aunt will be down soon, she adds that Nuttel must "must put up with me Vera)" in the meantime. In doing so, she creates an opening for her mischief but doesn't tip her hand.

An adept storyteller with a huge imagination, Vera utilizes all the details she needs to create a sense of realism: the open window, the brown spaniel, the white coat, and even the mud of the supposed bog are real and essential details..... the lead Framton to believe every word. The realism of the tale opens Framton up to the lies that accompany the reality.