I had wondered about the gap between the 1891 census / Samuel George's 1891 birth and Thomas's death in 1896. No more kids?
So I looked at FreeBMD for Puplett births in Wandsworth reg dist in that period, and lo and behold:
Joseph Puplett, December quarter 1893
I wonder whether he is the Joseph Pupplett in South Metropolitan District Schools, Sutton, Surrey, in 1901. In fact, there is a whole list of Pupletts there:
James, 1888 Battersea
Joseph, 1890, not known
Samuel, 1891 not known [is this your Samuel George?]
Thomas, 1892 not known (age corrected by you? from 1882)
Edward, 1893 Battersea
(James, Thomas and Joseph are on the same page.)
Now what you said was:
four children: Mary Rosina 1885, Thomas Jas 1886, John Edward 1889 & Samuel George 1891.
I have found her sons Thomas, John & Samuel in 1901 (Thomas with his paternal GM, John & Sam in Industrial School, no sign of Mary Rosina)
so I'm not sure whether this is fitting in or not. I don't see another Sam in 1901, for instance, and I don't see a match for John 1889.
A Thomas Samuel W Puplett was born in Greenwich in 1890 who could account for the Thomas in that list. But no, he was with parents Joseph and Jane in 1891 in Greenwich and grandmother Sarah Dixon in Woodville in 1901
Anyhow, just wondering whether you'd considered the possibility of other births after 1891, and whether that might help find Mary if maybe she had a younger child with her. No luck so far ...