In 1906, in her role as the title character in an adaptation of "Leah, the Forsaken", O'Neil recreated the role made famous by Italian actress Adelaide Ristori. Her performances in "Leah" (an adaptation of a translation of Salomon Hermann von Mosenthal's "Deborah") were described as "genius" by Fremont Older. She also appeared in "Trilby", "Camille", "The Common Standard", "The Wanderer", "Macbeth", "Agnes", "Sappho", "The Passion Flower", "Hedda Gabler", and many other productions in the United States and Europe. In 1908 a theatre critic for "The New York Times" shared his opinions regarding O'Neil's acting talents, providing what he viewed as both the strengths and weaknesses of her performances: