As you experienced, this is tough case.
Do you happen to know how old Kate was in 1919?
Ladysisland is a civil parish in southeast Co. Wexford.
I looked at the census records in the area and located this 1911 census record http://www.census.nationalarchives.ie/pages/1911/Wexford/Lady_s_Island/C... No Catherine or Kate shown but the parents had eight children and James was a tailor which could be construed as a shopkeeper.
I did find this 1881 birth record see fourth record https://civilrecords.irishgenealogy.ie/churchrecords/images/birth_return...
If Kate was 38 in 1919, I think this is the family.