The address in 1861 is indeed 5 James Terrace, Plumstead, so you have the right entry but you only have the first page not the continuation on the second page. I actually just noticed on the second page they also have a visitor called Emily Vines (age 17, born in Cambridge), who I guess might be related to Mary Jane?
Managed to find the continuation page on FamilySearch eventually, it is:
"England and Wales Census, 1861," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:Q2MG-GG4R : 10 December 2017), Mary Ann Middleton, Plumstead, London, Kent, England; from "1861 England, Scotland and Wales census," database and images, findmypast (http://www.findmypast.com : n.d.); citing PRO RG 9, The National Archives, Kew, Surrey.
It looks like their address in 1871 says Reclamation Works in Barking, Essex. I think it might be http://www.barkinghistory.co.uk/barking-sewage-works.html