She was involved in charity work throughout her life, operating a school and orphanage until her marriage to John Fletcher.

She and a friend, Sarah Crosby, began preaching and leading meetings at her orphanage and became the most popular female preachers of their time.

[1] Fletcher was known as a "Mother in Israel", a Methodist term of honour, for her work in spreading the denomination across England.

[3] However, Fletcher's older sister then introduced her to a member of the London Foundery Society, a Mrs Lefevre.

[13] This, along with her rejection of wealth and her parents' fear that she would convert her brothers to Methodism,[14] led her family to ask her to leave.

[18] Ryan had worked at Kingswood, and so provided the expertise Fletcher needed in order to set up a similar school.

[19][17] Over time, other Methodist women joined Fletcher and Ryan in their efforts, including Sarah Crosby and Mary Clark.

[21] The children were taught manners, reading, religion, writing, nursing and domestic skills to prepare them for later life.

[24] She would invite sick women into The Cedars to be treated by her; some stayed after being healed to assist Fletcher in her efforts.

[25] Bosanquet and Sarah Crosby instituted nightly Scriptural readings and prayer,[19] as there was no Methodist society in Leytonstone.

[26] To improve the religious environment in the orphanage, the women asked John Wesley to supply them with a preacher.

[19] Fletcher and Crosby continued to hold their own religious services on Thursday nights and began to attract large crowds.

[28] When Fletcher and Ryan first moved in, a crowd of villagers would throw dirt at anyone coming out of the house and yell at and spy on the residents.

[36] The move from The Cedars to Cross Hall was made to decrease costs, as the women were to grow their own food, to give the children a more pleasant environment, and hopefully to improve Ryan's failing health.

[2] While living and working at The Cedars, Fletcher, with Sarah Crosby, began to hold Methodist meetings at night.

[40][19] In the summer of 1771, Fletcher wrote to John Wesley to defend their work, now continuing at Cross Hall.

[44][45] However, it has been argued by the scholar Thomas M. Morrow that Wesley only allowed women to preach because they were successful in converting people.

He did not have a change of heart, and did not allow women to preach in order to make any sort of statement, only as a technique for expanding his denomination.

[40][48][49] Several times in her life, Fletcher's friends encouraged her to become a travelling preacher, due to her success and ability, but she did not take up the idea and found her passions to be more centred locally.

[52] At this time he considered proposing to Miss Bosanquet but decided against it, thinking she was too rich to accept and it would be better if he devoted himself to God.

[54] She and Fletcher moved to Madeley, Shropshire, on 2 January 1782 and started a joint ministry there as what was considered the first "clergy couple" among the Methodists.

[65] In 1793, Fletcher discovered a lump in her breast, which she tried to dissolve by praying and taking goosegrass juice as a herbal remedy.

[40] Her last sermon was given on 25 July 1815,[17] and three months before her death she ceased also to take religious meetings and hold classes.

[40][17] Mary Fletcher died on 9 December 1815, and was buried at St Michael's Church, Madeley, in a shared grave with her husband.

Reports have shown that the churches at Madeley were more popular than those in neighbouring regions even as late as 1851, 36 years after Fletcher's death.

[74] Thoughts on Communion with Happy Spirits (1785) discusses the death of her husband,[74] pondering whether he is still with her in a spiritual sense.

Dated 8 June 1794, the sermon was delivered in the vicarage at Madeley and speaks of being faithful and loving towards God.

Moore spliced the biography[70] together with her letters and diary entries and published them as an anthology entitled The Life of Mrs. Mary Fletcher.