Mrs. Vance lives across the hall from Carrie and Hurstwood's New York apartment. She and her husband are fairly well off, and Carrie is seriously envious of her extensive wardrobe and jewelry collection:
She seemed to have so many dainty little things which Carrie had not. There were trinkets of gold, an elegant green leather purse set with her initials, a fancy handkerchief, exceedingly rich in design, and the like. (31.53)
Boy, can this woman accessorize.
Hanging out with Mrs. Vance makes Carrie painfully aware of her diminished economic circumstances. She also further fuels Carrie's desire for stuff, which is a key issue in the novel. As the narrator notes, Mrs. Vance's clothes "augment[ed] Carrie's dissatisfaction with her state" (31.53). Carrie's jealously of Mrs. Vance also highlights the novel's concern with the factors that undermine relationships and create estrangement between people.