Bryant’s father is Rev. Dr. William Willock DD, Fellow and Tutor of Trinity College, Dublin. She is educated at home, largely by her father. As a teenager she moves to London when her father is appointed Professor of Geometry at the University of London in 1863, and she attends Bedford College. At the age of nineteen she marries Dr. William Hicks Bryant, a surgeon ten years her senior, who dies of cirrhosis within a year.
In 1875 Bryant becomes a teacher and is invited by Frances Mary Buss to join the staff of North London Collegiate School. In 1895 she succeed Buss as headmistress of North London Collegiate, serving until 1918.
When the University of London opens its degree courses to women in 1878, Bryant becomes one of the first women to obtain First Class Honours, in Mental and Moral Sciences, together with a degree in mathematics in 1881, and three years later is awarded the degree of Doctor of Science. In 1882 she is the third woman to be elected to the London Mathematical Society and is the first active female member, publishing her first paper with the Society in 1884. Together with Charles Smith, Bryant edits three volumes of Euclid‘s Elements, for the use of schools (Euclid’s Elements of Geometry, books I and II (1897); Euclid’s Elements of Geometry, books III and IV (1899); Euclid’s Elements of Geometry, books VI and IX (1901)).
Bryant is a pioneer in education for women. She is the first woman to receive a Doctor of Science in England, one of the first three women to be appointed to a Royal Commission, the Bryce commission on Secondary Education in 1894–1895, and one of the first three women to be appointed to the Senate of the University of London. When Trinity College Dublin opens its degrees to women, she is one of the first to be awarded an honorary doctorate. She is also instrumental in setting up the Cambridge Training College for Women, now Hughes Hall, Cambridge. She is also said to be one of the first women to own a bicycle.
Bryant is interested in Irish politics, writes books on Irish history and ancient Irish law (Celtic Ireland (1889), The Genius of the Gael (1913)), and is an ardent Protestant Irish nationalist. She is president of the Irish National Literary Society in 1914. She supports women’s suffrage but advocates postponement until women were better educated.
Bryant loves physical activity and the outdoors. She rows, cycles, swims, and twice climbs the Matterhorn. She dies at the age of 72 in a hiking accident in the Alps near Chamonix, France on August 14, 1922.