There is a birth reg in the Sep-Dec qtr 1885 for a Mary Louisa in the district of Spalding, 7a, 388a (
www.freebmd.org).
1901 census - Holts Lane, Hilgay, Norfolk (RG13/1894, Folio 58, Page 16)H.E. Burnett, Head, Wid, 62, Norfolk, Southery
Mary L " , Dau, S, 15, Servant Domestic, at home, Lincs Spalding
1891 census - Powderblue Cottage, Eye, Peterborough, Northamptonshire (RG12/1232, Folio 101, Page 7)Thomas Dunnett, Head, M, 51, Farm Labourer, Norfolk Hackford
Hannah " , Wife, M 51 " , Southery
John " , Son, 14, Farm Boy " , Fettlewell
George " , " , 13 " " , "
Mary " , Dau, 5 Lincs, Spalding
This all fits in with the 1881 census you have, it is possible that the Mary in that census had died and named the daughter in 1886 after her.
Kath