She was active in works of charity but she had failed to find a religious institute devoted to charitable work. She shared this idea with Archbishop Murray, Bishop Coadjutor of Dublin who was a friend of O'Brian. Murray returned later and said that he would bring a French order to Ireland if Aikenhead would lead it. To prepare for this task she became a novice from 1812 to 1815 in the Convent of the Institute of the Blessed Virgin at Micklegate Bar, York. She there assumed the name she kept till death, Sister Mary Augustine, though always known to the world as "Mrs. Aikenhead". `