Hi David
I found the digital images of the passenger list for the 'John Davis' on the Queensland State Archives website, assisted immigration 1848-1912. There are no full pages of individuals.
No I have not found Sophia on the 1851 census for certain. There is a possibility that a housemaid in the home of Robert Claque, a cooper of Darbyhaven is her. Class: HO107; Piece: 2526; Folio: 40; Page: 13; GSU roll: 105992-105996. Or maybe she is on another one of those unreadable images in Manchester. I am reasonably convinced that wherever she is, that Margaret Caley will be there too.
Thanks again
Maureen