This quote comes from early on in the book, when Claudia, Pecola and Maureen are out together. The implications of this image relate to the way white beauty is presented as being the ideal, but also completely inaccessible to African Americans. Note the way that the picture of Betty Grable, who was a white actress famous for her beauty and blond hair, "smiled down at us." It is almost as if she is being compared to a god-like figure, and the way that she smiled "down" at the girls indicates at once the way she is idolised because of her beauty, but also the distance between the girls and Betty Grable which is impossible to cross because of their skin colour. Note the story that Maureen tells Pecola and Claudia after stating that she loves Betty Grable:
My mother told me that a girl named Audrey, she went to the beauty parlour where we lived before, and asked the lady to fix her hair like Heddy Lamarr's, and the lady replied, "Yeah, when you grow some hair like Heddy Lamarr's."
Note how this anecdote supports the presentation of Betty Grable being a symbol of white beauty: incredibly idolised and desirable, but ultimately absolutely inaccessible. These girls are confronted, taunted even, by images of what they should be like if they want to appear beautiful in the eyes of society, but then have to reconcile themselves with the fact that they can never be "beautiful" in that way.