From Hangwomen.

It is reputed that in 1780 a middle aged woman from Co. Kerry called Elizabeth Dolan or McDermott was sentenced to death at Roscommon for the murder of her son. The town’s normal hangman did not turn up for the execution of Elizabeth and her 24 fellow condemned prisoners who were members of the “White Boys” so Elizabeth is reputed to have said to the sheriff “Spare me, yer Honour, spare me and I’ll hang them all.” As in law he would have had to have performed the task himself if no one else could be found, the sheriff agreed. Elizabeth executed her fellow criminals and was appointed Roscommon’s hang-woman and given a room of her own in the goal. She is thought to have operated there from about 1780 until her death in 1807. Her own death sentence was commuted in 1802.

Via Beachcombing’s Bizarre History.