A maid tells a man she is waiting for Willie, a sailor who left eight years ago. She would know him by a scar. He says Willie was killed in battle and told him to look after her. She only wants Willie. Then she sees his scar. They marry.
At the Reinhard Zierke site re Mike Waterson entry for Swansea Town: "A.L. Lloyd said in the Mike Waterson sleeve notes: Behind this is an Irish song, The Blooming Rose of Antrim. Old Phil Tanner, of the Gower Peninsula, South Wales, used to sing it, and perhaps it was he who moved the events to Swansea." It's Waterson's version that repeats the line "She's the blooming rose of South Wales and the Lass of Swansea Town."
However, the version of The Blooming Rose of Antrim I've seen, at Henry's Songbook site, called Flower of Corby's Mill, the form of the ballads is similar and there are some parallel verses but the stories are entirely different: specifically, Antrim has no mention of a lost sailor or his return; the "Blooming Lass" is "the bonny wee lass that works in Corby's Mill."
The CD _A Gower Garland_ by CaLennig includes (Tanner's?) version of "Swansea Barracks" in which the action takes place at Swansea Barracks but the maid is "the blooming rose of South Wales, the lass of Swansea Town." Swansea is in fact in South Wales. Antrim is in Northern Ireland.
As to moving the events to Swansea, it appears from the three Bodleian broadsides, which predate Tanner (1862-1950), that you were to substitute any barracks name you could make into two syllables and the "blooming rose" is equally non-differentiating.
In broadsides Harding B 11(2071) and Harding B 11(2072) she's "the blooming rose of England"; in Peacock "she appeared to be some goddess." - BS