Sentence:  "So you're going back to college in a fortnight," I said to the <WSD>Bright Young Thing</WSD> on the veranda of the summer hotel. "Aren't you sorry?" / "In a way I am," she said, "but in another sense I'm glad to go back. One can't loaf all the time." . . . / How full of purpose these modern students are, I thought to myself. 
Meaning of the word marked with <WSD> tags:  One who is youthful, clever, eager, and high-spirited in manner and attractive in appearance.