Her main subjects were women and children. When photography began to inch its way into fashion advertising, she made the transition by exhibiting her work at local galleries gradually establishing a solid career as a fine artist. Immensely popular with the public, her life-like portraits were widely coveted, and she began to feel the pressures of keeping up with her growing number of portrait commissions where children and adults continued to be her subjects.
Over the years Hartley has felt equally at home working in several mediums – charcoal pencil, watercolor, and oil. In the 1990s she began exploring sculpture as well, energetically making it a capstone to a career that spans more than sixty years.