This is the baptism record for the Sarah Loftis who was born on 30 June 1794:
20 Jul 1794
St Dunstan and All Saints, Stepney, Tower Hamlets, Middlesex, England
Source: London, England, Church of England Baptisms, Marriages and Burials, 1538-1812 London Metropolitan Archives; London, England; Church of England Parish Registers, 1538-1812; Reference Number: P93/DUN/005
Viewing an image of the record it says she was 20 days old when she was baptised, which fits with the birth date of 30 June 1794.
This is probably not the same person as the Sarah Mayhew who died in 1881 in St Giles, as she was 80 when she died.
Of the 4 possible Sarah Mayhew deaths in Bethnal Green between 1851 and 1861 that Paula mentioned, it is definitely not the one who died in 1856 as she was aged 0. It is probably also not the one who died in 1860 as she was aged 60. It might be either of the others, as the one that died in 1858 was aged 65 and the one that died in 1859 was aged 66. (All ages at death from https://www.gro.gov.uk/gro/content/certificates/indexes_search.asp)