Born Sybil Anne Rivers in Atlanta, Georgia, she was raised in Fairburn, Georgia, and attended Auburn University, where she was a member of the Delta Delta Delta Sorority.

While at Auburn she wrote a column for the student newspaper, The Auburn Plainsman, that favored integration. The university administration attempted to suppress the column, and ultimately fired her, and the column garnered national attention. She later became a senior editor for Atlanta magazine.

At the age of thirty she married Heyward Siddons, and she and her husband lived in Charleston, South Carolina, and spent summers in Maine. Siddons died of lung cancer on September 11, 2019