Garrett was born in Oklahoma City on June 30, 1963 to Robert and Jane Garrett. According to her mother, Garrett began to read very early and thereafter was never seen without a book in her hand. At age 3, according to Jane, young Garrett announced she would be a lawyer—Garrett, more modestly, claimed she was 5. Her father, Robert, had earned a law degree, though he worked as president of a savings and loan. An uncle and grandfather were also lawyers.