In 1898, Horne was elected to the Utah House of Representatives representing the Salt Lake Eighth District. She served for one term and made many notable contributions in a short time. She advocated for many bills that eventually became law. While many of them revolved around the arts and education, she did not limit her influence to those areas alone. While in the state legislature, she was a key force behind enacting a bill to create a state art institute and to create a state art collection. The latter is today named the after her. Professor William M. Stewart of the University of Utah brought a scholarship bill to her and asked for her help with it. It was passed, and by 1921 had provided more than 8,000 students with scholarships. Among others, Horne campaigned for a Public Health bill, an Art bill, and a Fish and Game bill. She served on the Rules, Public Health, and Education and Art committees during her term in office and was also chair of the new University Land-Site Committee that oversaw the acquisition for the current site of the University of Utah. In 1901, Horne was called as a member of the general board of the LDS Church's Relief Society. She served on the board until 1916 and during part of this time was chair of the art committee. In 1904, she served as a delegate on behalf of the Relief Society to the International Congress of Women held in Berlin, where she delivered two addresses. She served as president of the Daughters of the Utah Pioneers from April 11, 1903, to April 24, 1905. She was a leader and advocate in numerous other ways, including as a regent of the Daughters of the Revolution and the Chair of the Utah branch of the National Peace Society. Horne also played a role in organizing the Women's Chamber of Commerce in Salt Lake City as well as the Smokeless Fuel Federation. Horne authored two books at this time in her life: Devotees and Their Shrines and Columbus, Westward Ho!. The former is a handbook of Utah art and artists that aligns with her continual promotion of the arts throughout her life's work. A portion of her introduction to the book reads, "God has created gifts, and men work so that we are not without poets, painters, sculptors, architects, craftsmen, gardeners and home makers. So long as talent and industry unite there will be art—original, spontaneous, inspirational—the kind that lives. We are all artists to a degree, or at least let us believe that Providence so intended." Moving away from the description of art and towards the production of it, Horne's 1922 Columbus, Westward Ho! is the script of a play that she authored. Intended for young audiences, it is a retelling of the Christopher Columbus story. Starting in the 1920s, Horne ran an art gallery with the main goal of exhibiting and selling works of inter-mountain artists. Her husband died in 1934 and she continued to run the art gallery until her own death in 1948.
