Sillitoe was one of eight children born to Robert E. and Phyllis Liddle Buhler. She was reared in Salt Lake City, Utah and graduated from the University of Utah. She married John Sillito (spelling difference intentional), in 1968 and had three children.

Sillitoe was a staff writer for the Deseret News and news feature editor for Utah Holiday magazine. She produced articles which also appeared in The New York Times, The Philadelphia Inquirer, A Journal of Mormon Thought, Utah Business, Sunstone, City Weekly and The Salt Lake City Observer. She won awards from the Utah chapter of the Society of Professional Journalists and the Associated Press. Sillitoe received three nominations for a Pulitzer Prize for her stories about life in Salt Lake County.

Sillitoe co-produced a PBS-affiliated documentary, "Native and American" in 2003, and taught classes in journalism and writing at the University of Utah, Salt Lake Community College and Weber State University. She most recently worked as public outreach coordinator of Weber State University’s Stewart Library.

Sillitoe died on April 7, 2010, at the age of 61, of a heart attack after a long illness.

Sillitoe wrote three important books on aspects of Utah history: "Banking on the Hemingways: Three Generations of Banking in Utah and Idaho"; "Salamander: The Story of the Mormon Forgery Murders" (co-authored with Allen Roberts); and "Friendly Fire: The ACLU in Utah." In 1996 she wrote the official centennial history of Salt Lake County, published in a popular format as "Welcoming the World: A History of Salt Lake County."

Sillitoe published a collection of poetry "Crazy for Living," a short story collection "Windows on the Sea", and two novels "Sideways to the Sun" and "Secrets Keep." An additional novel awaits publication. Her creative works received awards from the Association for Mormon Letters.

Selected works

• Sideways to the Sun, 1987;
• Salamander: Story of Mormon Forgery Murders, editions published in 1988, 1989, 2006;
• Windows on the Sea and Other Stories, 1989;
• Banking on the Hemingways: Three Generations of Banking in Utah and Idaho, 1992;
• Crazy for Living: Poems, 1993;
• Secrets Keep, 1996;
• Friendly Fire: The ACLU in Utah, 1996;
• Welcoming the World: A History of Salt Lake County, 1996.