Sentence:  As she did so Fanny put down her book , stood up and stretched her arms, and at once Jessamy noticed a <WSD>difference</WSD>. It was the same Fanny but not the Fanny who climbed trees and tore her frock playing in the garden. It was as though a young lady film had settled over her, neatening her unruly hair, which was tied back with a large black bow, and primly composing her small mouth. 
Meaning of the word marked with <WSD> tags:  Significant change in or effect on a situation or state.