I checked the records and it looks there is a Mary Steel, dying in Crosscanonby in 1833 aged 37, giving her a birth date of about 1796, which is not a major gap from James's birth date of 1789.
If I could find a baptism for a Mary Landsbrough of Bromfield near that date, then that would confirm if its the right person.
In the Bromfield marriages, there is a marriage in 1823 of a Sarah Landsbrough of Bromfield, possible sibling? Mary married in 1826