if you are deriving your query from the 1841 census of a single household in Strand street with a sub househols of Wm Sayle + Jane Sayle (prob married couple) then I initially thought the Isabella Sayle in preceding sub household is Isabella Christian ?widow of John Christian however there is an Isabella Sayle als Christian bur German 18561222 age 73 who assuming transcription correct is too old to be mother of the child Isabella noted in bapts