The 1851 census for German - piece 2523, folio 235, schedule 18, has:
William Fargher, 12, German
Elizabeth Corkish, 6, German
Henry Lewney, 3, German

The relationship column has "Children belonging to Catherine Killey"

This would seem to indicate that Catherine was between 25 and 50, unmarried, at the 1851 census. I can find no such entry.

Elizabeth would seem to have been baptized 6 Jan 1845, father William Corkish.
Henry baptized 3 Oct 1848 at Ballaugh.

Any help in identifying Catherine Killey much appreciated.