A William Newman also married Ann Grossmith in 1868 and she appears on the 1881 Census as the step-sister (actually sister-in-law) of Thomas Brinsley. She was born in Longthorpe in the same year as Ann on the 1891 census.
Elizabeth Dicks on the 1881 census was also Grossmith of Longthorpe.
For info.
I think Elizabeth Dicks nee Grossmith may be dau of Thomas occ. Shepherd & Elizabeth but
she's not with them on 1841 c
edit she would't be as born c1845
she is with parents and older brother William 1851c HO107; Piece: 1747; Folio: 569; Page: 3
https://www.familysearch.org/ark:/61903/1:1:SGTY-TBFcan’t find baptism for Ann parents Thomas & Elizabeth
Elizabeth Grossmith
Baptism 6 Jul 1845 Peterborough, St John, Northamptonshire
Father: Thomas Grossmith occ Shepherd
Mother: Elizabeth abode Longthorpe
Bpt also at St John's
Lucy Grossmith 23 Sep 1832 father Thomas ,Labourer
Jane Grossmith 15 Nov 1835 " occ Shepherd
William Grosmith 29 Oct 1837
Mary Grossmith 7 Sep 1840
1841c HO107; Piece: 815; Enumeration District: 11; Page: 2
Longthorpe
Thomas Grossmith 30 occ Shepherd
Elizabeth 30
Lucy 8
ANN 6Jane 4
William 3
Mary 10 months – I think Mary marries a Thomas Brinsley they can be found on
1871c RG10; Piece: 1519; Folio: 33; Page: 7 with her Parents Thomas & Elizabeth Grossmith
https://www.familysearch.org/ark:/61903/1:1:VFF9-1MNADDEDThis might be Ann Grossmith from 1841 census on 1851/1861c occ employee/house servant
1851c
https://www.familysearch.org/ark:/61903/1:1:SG19-F8B1861c
https://www.familysearch.org/ark:/61903/1:1:M75G-9JG