rosie,
A tree on ancestry has her as Isabella Doust showing as Doutt in ancestry census records, born about 1760, and born locally to Greenwich from that 1841 census.
It then suggests this one:
Mary Kirby
Baptism Date: 2 Nov 1766
Parish: St Alfege County: Kent Borough: Greenwich
Parent(s): Richard Kirby, Barbara Kirby
Record Type: Baptism Register Type: Parish Register