Georgiana Moore was born in Dublin of Protestant parents on March 20, 1814, the daughter of George and Catherine Moore. Her father died in 1817, and "the family continued Protestant until 1823, when Mrs. Moore and her children [were] received into the Catholic Church" (Carroll, Leaves 2:37).

On August 23, 1844, Georgiana wrote that she "became acquainted" with Catherine McAuley in September 1828 and that she "went to reside in Baggot Street on the 13th October." Mary Bertrand Degnan says that Georgiana, then about fourteen years old, "came to Baggot Street in answer to a call for a governess" for Catherine's young niece, Catherine Macauley, and her adopted cousin, Teresa Byrn, ages nine and seven (75). Georgiana left Baggot Street temporarily in 1829, evidently in poor health. However, she returned on June 10, 1830, and remained there until she departed, at the age of twenty-three, to become the first superior of the Mercy community in Cork. Her sister, Clare Augustine Moore, writing to Bermondsey on July 7, 1875, says of her: "She entered. . . when she was little more than sixteen, not without a severe mental struggle. How she lived so long is wonderful for her lungs were diseased when she was fourteen and continued so for many years after, I know, perhaps to the last."

Georgiana Moore, who had stayed behind on Baggot Street when Catherine McAuley went to George's Hill, was among the first seven who received the habit of the Sisters of Mercy at Baggot Street on January 23, 1832, and one of the first four who professed their religious vows on January 24, 1833. She was then not quite nineteen years old. At her reception of the habit she adopted the baptismal name of her older sister Mary Clare (who later entered the Sisters of Mercy as Mary Clare Augustine Moore). Clare was an intelligent, trusted companion to Catherine McAuley and the person who most closely assisted Catherine to prepare the original Rule and Constitutions of the Sisters of Mercy.

On July 6, 1837, Clare became the first superior of the Sisters of Mercy in Cork. On November 21, 1839, she became the first superior of the Bermondsey foundation. This appointment was intended to last only a year, until Mary Clare Agnew was prepared to assume leadership. In June 1841, Clare returned to Cork where she resumed the role of superior. However, in the months that followed, Clare Agnew's grave misunderstanding of the ministerial vocation of the Sisters of Mercy threatened to destroy the spirit of the Bermondsey community; she was, therefore, removed from office and subsequently left the community. On December 10, 1841, Clare Moore returned to Bermondsey, at the request of Bishop Thomas Griffiths, and was re-appointed superior on December 13, 1841. From then until her death, except for fifteen months in 1851-1852, she was superior in Bermondsey.

"Her governing powers were extraordinary; as was once remarked of her [evidently by one of the bishops with whom she worked], 'she was fit to rule a kingdom'" (2:[225]).The work of the Bermondsey community was multifaceted. Under Clare Moore's leadership, they visited the sick poor in their homes and in Guy's and St. Thomas's Hospitals, instructed adults, prepared hundreds of children for their first Communion and Confirmation, conducted poor schools for female children and an infant school for toddlers, and visited the poor in their homes, providing material help and spiritual consolation. Clare was, for almost thirty-five years, the chief organizer of all these ministries. The Bermondsey Annals says of her: "Her governing powers were extraordinary; as was once remarked of her [evidently by one of the bishops with whom she worked], 'she was fit to rule a kingdom'" (2:[225]).

'The Mission of Mercy: Florence Nightingale Receiving the Wounded at Scutari' by Jerry Barrett, 1856–1858. National Portrait Gallery: NPG 6202. This photographic reproduction is considered to be in the public domain. Florence Nightingale, clearly highlighted in the centre of the group, is shown receiving casualties in the courtyard of the Barrack Hospital at Scutari. Mother Clare Moore can be seen to the left  of Florence Nightingale.

On October 17, 1854, Clare with four other Bermondsey sisters went, on three days' notice, to the Crimea to nurse the sick and wounded British, Scottish, Welsh, and Irish soldiers who were involved in the war with Russia. In early 1856 three more sisters from Bermondsey joined them. Clare was assigned to the Barracks Hospital in Scutari, Turkey, and worked there until peace was declared. But having become dangerously ill, she left Scutari before all the wounded returned home, arriving back in Bermondsey on May 16, 1856. In the Crimea, the Bermondsey sisters served under the superintendence of Florence Nightingale. On April 29, 1856, the day after Clare left Scutari, Miss Nightingale wrote to her from Balaclava:

Your going home is the greatest blow I have had yet. . . . You were far above me in fitness for the general superintendency, both in worldly talent of administration, and far more in the spiritual qualifications which God values in a superior. My being placed over you in our unenviable reign of the East was my misfortune and not my fault. I will ask you to forgive me for everything or anything which I may unintentionally have done which can ever have given you pain. . . . Ever my dearest Revd. Mother's
(gratefully, lovingly, overflowingly)
Florence Nightingale

Florence Nightingale and Clare Moore remained close friends and corresponded until Clare's death.

In England, Clare's remarkable skills—of nursing, consoling, teaching, administering, and writing - served hundreds of people, the neglected and the well known, including the bishops of London and Southwark. It was she, and other sisters from Bermondsey, who "day and night" attended the severely ill, and now almost blind, Bishop Thomas Griffiths, Vicar Apostolic of the London District, before his death on August 12, 1847. Clare herself evidently stayed with him each night for over two weeks. She also worked with Cardinal Nicholas Wiseman, Bishop Griffith's second successor, and with Archbishop Henry Manning. But the bishop with whom she collaborated most closely was Thomas Grant, Bishop of Southwark from 1851 until his death in Rome, at the Vatican Council, on June 1, 1870. A wealth of archival material in the Bermondsey archives, including correspondence, documents their relationship. Clare served as a secretary and translator for Bishop Grant. Their working relationship and mutual respect contributed steadily to the accomplishments of both. When Clare was dying, Bishop James Danell, the new Bishop of Southwark, "visited her every day and left with her his pectoral cross, which contained a relic, and which formerly had belonged to the revered Bishop Grant" (Bermondsey Annals 2:[228]). After her death, Rev. William Murnane described Clare's life as "a humble, unobtrusive life, yet full of sublime self-sacrifice and painful labour in the cause of God, doing far more for him and suffering humanity than the accumulated acts of many others" (Bermondsey Annals 2:[230]).

"I do not imagine that many of our Institute will celebrate their whole jubilee - our work takes away strength too surely. And the clergy do not think of that in many places, where our Sisters are often overburdened with work, day and night - no cessation, no rest, for mind or body" (Carroll, Leaves 2:108). During her years in London, Clare Moore and the Bermondsey community founded eight additional autonomous houses in England: Chelsea (1845), Bristol (1846), Brighton (1852), St. Elizabeth's Hospital for Incurables on Great Ormond Street, London (1856), Wigton in Cumberland (1857), Abingdon (1859), Gravesend 1860), and Clifford (1870) where they replaced the Dublin sisters, as well as a branch house in Eltham (1874). St. Elizabeth's Hospital - later called Saints John's and Elizabeth's - was founded on November 19, 1856, the first Catholic hospital in London since the Reformation. In 1873, Clare wrote: "I do not imagine that many of our Institute will celebrate their whole jubilee--our work takes away strength too surely. And the clergy do not think of that in many places, where our Sisters are often overburdened with work, day and night - no cessation, no rest, for mind or body" (Carroll, Leaves 2:108). Nonetheless, Clare was a generous correspondent, and many of her autograph letters are preserved in the Bermondsey archives.

The Bermondsey Annals for 1874 reports her personal involvement in establishing the Eltham house, her last major endeavour on behalf of the English poor.

On September 23rd . . . Canon Wenham came, on behalf of the Bishop, to ask Revd. Mother if she would take charge for him of a Girls' Industrial School at Eltham, which had fallen into a very deplorable state. . . . On Sept. 30th Rev. Mother. . . went to Eltham to take possession and begin the new work. No words can describe the dirt and disorder that everywhere prevailed. . . . The place had been stripped of everything but 25 bed steads with their miserable straw mattresses and thread-bare coverings. There were 25 neglected looking girls, who had hardly a change of clothing. . . . (2:[222-24])

Clare lived only ten weeks longer. On December 2, 1874 she caught a cold but claiming that "a cold doesn't last forever," she rallied (Carroll, Leaves 2:268). However, on December 6, a doctor diagnosed her condition as pleurisy, and on December 14,1874 she died in Bermondsey, in her sixty-first year. About a month before her death, she wrote, with generosity and humour, about the Eltham situation:

We have been obliged to take from our own barely sufficient quarter's income almost half. We had to buy necessary furniture, and you would be amused at the scanty supply; clothing for the poor children, whose garments are next to rags; bed-covering and food, besides begging three months' credit from butcher, baker, grocer, etc.; afraid to light fire enough to warm us or cook our provisions. . . . One [child] only eight years old had stolen a perambulator with a baby in it; another a waterproof, which she sold at a rag shop. What a blessing for these to be with us, but what an anxious charge for us! . . . I have been there six or seven times - no little cross to me, who do not care for travelling. We must accept our cross whatever it is made of, even a railway carriage. (Carroll, Leaves 2:268)

Clare Moore was, throughout her life, one of the outstanding co-founders of the Sisters of Mercy, and a remarkable, though unrecognized, contributor to the mission of the Catholic Church in England. She also authored three important documents on the early history of the Sisters of Mercy: a set of five letters about Catherine McAuley to her sister, Mary Clare Augustine Moore, from August 23, 1844 through August 26, 1845; a long biography of Catherine McAuley entered into the Bermondsey Annals for 1841; and the first publication of A Little Book of Practical Sayings, Advices and Prayers of Our Revered Foundress, Mother Mary Catharine [sic) McAuley (London: Burns, Oates & Co., 1868)