 O'Mahoney attended for several years the school of the Sisters of Notre Dame, St. Mary's School, and later she took the course in the Lawrence High School, graduating with the highest honors of her class in 1873.She was also taught by private tutors.O'Mahoney taught in the Lawrence High School from 1873–92, filling the position of teacher of history, rhetoric and elocution, including teaching poetry to Robert Frost.