There is a WH record 1875 for Emma Preedy - Westminster.
I think this may be a red herring. This Emma Preedy was discharged from the Westminster workhouse in 1875 to the Hanwell Asylum, and the target Sarah (Emma) Preedy has been found at home in 1881.
Also, although this record is a Westminster workhouse, it’s the wrong union (ref. WEBG/WM/054/004). The reference for the
Strand Union is WEBG/ST....
For anyone who wants to check manually, A&D records for the
Edmonton workhouse are on Ancestry under
London, England, Workhouse Admission and Discharge Records, 1764-1930 > Westminster > Westminster > Edmonton Workhouse Register, 1870-1902.
ADDED - There may also be
unindexed records for the Strand Union browsable in Ancestry’s other database -
London, England, Poor Law and Board of Guardian Records, 1738-1926.
If nothing relevant is found, you might also want to consider whether William Preedy's second marriage may have been bigamous, which was not uncommon in London at this period.