This is shoddy nonsense, I am afraid.
There is a reference by Joseph Plumb Martin to an unknamed woman helping serve a gun at Monmouth Courthouse in 1778. No mention of water.
We have Margaret Corbin, a pensioner who was wounded at the side of her gunner husband at Fort Washington in 1776. Later known as 'Captain Molly', she died in 1800 long before the Molly Pitcher story first emerged.
That's it.
There is no mention of Mary McCauley (she remarried) at Monmouth CH during in her lifetime, nor any description of any actions corresponding to the legend. While the presence of Mary Ludwig Hays with the army in 1777-78 is recorded, there is no evidence for the role she allegedly performed at the battle of Monmouth CH, either serving water to the troops or taking her husband's place manning a cannon. There is only mid-C19th hearsay.
When the remarried 'Mrs Molly MacCauley' died in 1832, her obituary in local press recorded only "She lived during the days of the American Revolution, sharing its hardships, and witnessed many scenes of blood and carnage. To the sick and wounded she was an efficient aid." </>
If, as claimed 20 years later, she was "the remembered heroine, the celebrated "Molly Pitcher, "pointed out in the street as 'the woman who fired the cannon at the British when her husband was killed," that fact was overlooked in her obituary. By 1876, it was being claimed in addition that she had been buried with military honours; a fact also overlooked in Molly MacCauley's obituary
What we do have is the documented service of Margaret Corbin, wounded while serving a gun in the defence of Fort Washington in November 1776 and who, as 'Captain Molly,' lived out her life as a pensioner at West Point, dying in 1800.
Joseph Plumb Martin's account, published in 1830 (fifty years after the event), mentions an unnamed womam serving a gun at Monmouth CH. No reference to water.
The figure of 'the famed Captain Molly at Monmouth ' who downed her pail of water to replace her dead husband manning a gun at Monmouth CH and was saluted by Washington, is not found recorded before 1830: '"While Captain Molly was serving some water for the refreshment of the men, her husband received a shot in the head, and fell lifeless under the wheels of the piece. The heroine threw down the pail of water, and crying to her dead consort, ‘lie there my darling while I avenge ye,' grasped the ramrod, … sent home the charge, and called to the matrosses to prime and fire. It was done…."
Coincidentally, 1830 was the year that the first version of Joseph Plumb Martin's published journal saw the light of day.
In 1841 we find the first reference to a "Moll Pitcher, the Heroine of Monmouth." Only in 1856, is Molly McCauley first referred to as "the celebrated "Molly Pitcher."