Hi Caroline
Just to confirm your findings on the cert are untrue this is the 1861 census.
I would get the Reg Office that sent you the copy of marriage cert to check the entry as it could be a hand written copy by the current registrar and their eyes may just have wondered down the entry a bit as the witness name also appears to be Grace.
If this is the case maybe tehn they shold by right rectify the mistaek free of charge.
Eliza Gillard abt 1849 South Tawton, Devon, England Daughter South Tawton Devon
Elizabeth Gillard abt 1845 South Tawton, Devon, England Daughter South Tawton Devon
Ellen Gillard abt 1858 South Tawton, Devon, England Daughter South Tawton Devon
Emma Gillard abt 1855 South Tawton, Devon, England Daughter South Tawton Devon
George Gillard abt 1815 South Tawton, Devon, England Head South Tawton Devon
Maria Gillard abt 1860 South Tawton, Devon, England Daughter South Tawton Devon
Mary Ann Gillard abt 1817 South Tawton, Devon, England Wife South Tawton Devon
Good luck with sorting it out.
Wendy