A native of Salt Lake City, Utah, Arnold received bachelor's and master's degrees from BYU. Arnold also holds a Ph. D. from the University of Wisconsin–Madison. She is a leading scholar on the work of Willa Cather having written among other works A Reader's Companion to the Fiction of Willa Cather and Willa Cather's Short Fiction. Arnold also studied the works of other authors who set their works in the great plains states. Arnold was also closely involved with work relating to poetry. Arnold also wrote on the works of Milton.
Arnold has written eight novels including Minding Mama and also Sacred Hymns from the Book of Mormon with Maurine Ozment and Lisa Farr.
Prior to joining the BYU faculty Arnold was a professor at Weber State University.
Arnold has also served as the head of the Center for the Study of Christian Values in Literature at BYU. Arnold is a Latter-day Saint.