This dress represents the femininity that Gene's mother wants her to have. Gene does not wear a lot of dresses, she prefers dressing as a boy. Gene's mother wants her to be the perfect woman to find a suitable husband and to help her family move up from their current social class. The dress represents who Gene's mother wants her to be, "Mother had forced me to wear a horrible confection of a dress, with froths of white lace and a wide pale-pink sash high around my corseted waist" (Lam, 79).
Not sure if dress is truly vintage or not because this pin lacked a date, but if it is then I'm guessing it's from the first half of the 19th century. I'd welcome input from someone more knowledgeable.