A key aspect of 18th c gossip is total anonymity. When the great portraits were hung in the Royal Academy the titles would only be listed as "a man" or "a woman," etc. Crowds would gather and test each others' pop culture based on whether they could identify the sitter or not. The tabloids of the times, satirical prints, kept their subject anonymous many times too, despite the newly freed press. Sometimes, for gossip's sake, instead of listing the subjects name the satirical artist would just drop a subtle hint, "A certain dutchess..."
Because Georgiana was a leader of the ton and a leading female celebrity most everyone knew who she was and what she did. Therefore, artists developed a means of identifying Georgiana in their work so viewers would know who the anonymous scandalous lady was.
The most popular identifier was Harriet. If a work contained two tall, poufy-haired, fashionable ladies next to each other it was Georgiana and her sister. Despite Bess being Georgiana's best friend, society found the two sisters to be inseparable (they were) and they would constantly be seen in public together. Just like in this print by Rowlandson:
The second article of identity was a dog. Yes, dogs were popular in the 18th century, but their biggest fan was Georgiana's husband, whom was called Canis by his friends. There is a family tradition of the Dukes and Duchesses of Devonshire being obsessed with their dogs and still remains true today -their furry family is usually part of their portraits. The association of Cavendish/Dog made for another identifier for Georgiana as can be seen in this print Robert Dighton did of the 1784 Westminster Election:
Feathers, feathers, feathers! Can you imagine if you popularized shoulderpads in the 1980's and you were still being depicted wearing those awful 80s blazers today? What a nightmare. Well, if you recall, Georgiana popularized the fad of huge ostrich feathers in the late 1770's. For ever afterwards she was depicted as wearing them in her hair.