Alice Prin (1901-53), better known as Kiki de Montparnasse, was the archetypical artist's model / bohemian bon vivante of 1920s Paris. Never-married, her best-known companion was Man Ray, who painted in Dada-Surrealist modes but is best known as a photographer ranging from experimental work to high fashion. He took many pictures of Kiki, some of which are indeed iconic.
I found biographical information about her on the Internet to be rather skimpy. Here is her Wikipedia entry in English and the French entry is here. Neither is truly informative, though the general path of her life is sketched. A source I like is this book which contains a decent amount of text along with scads of fascinating photos of Kiki and many of the rest of the arty crowd that inhabited the Left Bank; the coverage is roughly 1900 to 1930.
The Internet offers many photos of Kiki, but not a lot of paintings. And many of those painting are of her "in the nude" as it was once politely phrased -- she was an artist's model, after all. Nevertheless, below are a few photographs to set the scene, followed by interpretations of her face by various painters.
Gallery
Note that even the photographs show that Kiki's appearance was elusive. In part this had to do with camera angle, lighting and whatever makeup she was wearing. Otherwise, her shape changed over the 1920s as she got older and added weight: note how she looks in the Kertész photo (and how Krogh slimmed her down).