Betsy Gray goes to Ballynahinch battlefield. She finds her wounded fiance Willie and brother George. A Yeoman sword cuts off her hand as she pleas for her brother's life. Another Yeoman shoots her. The bodies are found and they are buried in one grave.
Hayward-Ulster has Betsy fighting beside Wullie Boal and her brother George. "When adverse fate with victory crowned the loyal host upon that day, Poor George and Wullie joined the flight, and with them lovely Betsy Gray." Their fight, wounding, and death follows. - BS
For the Battle of Ballynahinch, see especially the notes to "General Monroe." The battle was the last stand, or nearly, of the Ulster portion of the 1798 rebellion. The rebels had hardly fought; their lack of discipline caused them to collapse when pressed by the loyalist forces of General Nugent.
It appears this song is essentially accurate; Thomas Pakenham, in _The Year of Liberty_ (which generally downplays the worst behavior by British troops), p. 231, reports that "[no] one knew how many rebels had been killed, but it was assumed about four hundred. The bodies lay unburied in the deserted streets of Ballynahinch, like those at New Ross the week before, food for the local pigs. Other victims of the battle were taken away by night and buried by their relatives. Among them was a young girl called Betsy Gray, who was later to be famous for her part that day. She had fought beside her brother and lover, and they had stayed by her in the retreat, although they could have outridden their pursuers; all three were shot down by the yeomanry."
A. T. Q. Stewart, _The Summer Soldiers: The 1798 Rebellion in Antrim and Down_, Blackstaff Press, 1996, p. 227, reports that "A young woman called Elizabeth Gray, with her brother George and her fiance, Willie Boal, were aboyut to cross the country road when they were apparently seen by a vedette posted at the nearby crossroads. The scene of the encounter was a marshy hollow at Ballycreen, about two miles from Ballynahinch. Betsy Gray (to give her the name by which she is best remembered) had gone ahead of the men and was taken first. When George Gray and Boal went to her aid they were instantly shot down. Then a cavalryman called Jack Gill struck off the girl's gloved hand with his sabre, and Thomas Nelson 'of the parish of Annahilt, aided by James Little of the same place' shot her through the head.... Young Matthew Armstrong found the mutilated bodies, and with the help of two neighbours carried them to a hollow on his property, and buried them there in a single grave, 'leaving those faithful Hearts of Down sleeping the sleep that knows no waking.'"
Much folklore arose as a result, including some versions in which Betsy became the beautiful commander of a force of rebels. Her story eventually inspired Wesley Greenhill Lyttle to write the popular (but not especially accurate) novel _Betsy Gray, or The Hearts of Down_ (1886). - RBW