In 1808, Mary went to stay with her friend Anne O’Brien in Dublin. Here she witnessed widespread unemployment and poverty and soon began to accompany her friend in visiting the poor and sick in their homes. From this experience she believed it would be her vocation to help the sick and the poor as a member of a religious Community. She trained for 3 years (1812-1815) in a convent in York, England in order to become a Nun. When she returned to Dublin she set up the Religious Sisters of Charity in Ireland.
On 1 September 1815, the first members of the new institute took their vows, Sister Mary Augustine being appointed Superior General. Added to the traditional three vows of poverty chastity & obedience, was a fourth vow: to devote their lives to the service of the poor. For the next 15 years Mother Mary worked very hard to alleviate the sufferings of the less well-off but it took a terrible toll on her own Health.
However she did not let her own personal misfortune get her down:
“Low spirits and dreads of evil to ourselves or Congregation, or even to the church, are actually the beginnings of despair. If all the rest of the world goes wrong, we should still persevere in trying to serve our God with faith and fervour.” (7 November 1834)
Confined to bed or a wheelchair she continued to direct her charges and set up new institutions both at home and abroad. Her Sisters were particularly active during the great Cholera outbreak in 1832. She died in Dublin, aged 71 in Our Lady’s Mount Harold’s Cross and was buried in in the cemetery attached to St. Mary Magdalen's, Donnybrook, Dublin 4.
Her cause for canonization as a saint has been progressing in Rome. On 18 March 2015, a decree was issued proclaiming her heroic virtues. This entitles her to be referred to as the Venerable Mary Aikenhead.