How Fitzgerald knew the ways girls are and act we'll never know. He captured the moments perfectly. In such a detailed manner too. This here was my favorite passage in Bernice bobs her hair;
Downstairs she opened the big front door, closed it carefully behind her, and feeling oddly happy and exuberant stepped off the porch into the moonlight, swinging her heavy grip like a shopping-bag. After a minute's brisk walk she discovered that her left hand still held the two blond braids. She laughed unexpectedly- had to shut her mouth hard to keep from emitting an absolute peal. She was passing Warren's house now, and on a impulse she set down her baggage, and swinging the braids like pieces of rope flung them at the wooden porch, where they landed with a slight thud. She laughed again no longer restraining herself. "Huh!" She giggled wildly. "Scalp the selfish thing!" Then picking up her suitcase she set off at a half-run down the moonlit street.
What a delightful stretch of words. Marjorie deceives Bernice into getting her hair cut into a bob and almost shames her in front of the whole crowd. So Bernice cuts her hair, giving Marjorie-the-bad-word a bob.