Thanks for all your suggestions. I think I have all I can get out of this and believe I have the correct Dorothy Marshall and her mum as Catherine.
As a side note and to link things together, Dorothy Marshall is found in 1851 aged 2 at Hill Gate with the Browns as a granddaughter, and her mum working as a servant just over the river in Newgate Street. In 1861 she is away elsewhere, and I cannot find her in 1871. In 1881 after marrying William Martin, she is back again to Hill Gate, so I am currently hunting out maps to see how close the houses were, but they are both near the start of the count from Wansbeck Street. In 1891 they are found at Newgate Street, again checking maps to see if there is any connection where Catherine was in 1851.
So all thats left to find is Dorothy in 1871 and what the connection is to the Browns.
