The writer was looking for inspiration when pal Tate Taylor introduced her to the actress and the idea for Mississippi maid Minny Jackson was born.
Taylor went on to direct the movie adaptation of the bestseller and Spencer was the only actress who didn't have to audition for him.
In fact, the director and his star have been longtime friends and once shared an apartment.
The film, also starring Bryce Dallas Howard, Emma Stone and Viola Davis, is well on its way to becoming the sleeper hit of the summer after taking in over $10 million (£6.25 million) in just a day. The movie was released in the U.S. on Friday (12Aug11).