I am having a bad day regarding re-search, and would appreciate some help please.

Grace is living with her parents in 1861, Benjamin Toman Thomas born in St Just 1812 and wife Ann 1816 born Madron....after his death Ann uses the name Nanny on the census.
RG9 1598 F86 Page 9
Although I spot an unmarried mother who could be Grace Thomas in 1871, the next positive sighting of her is in1891.
!891 St Just.
RG 12/1860 F186 Page 17.
Nanny Thomas Head/W/74 born Madron
Grace
EDDY/dau/W/52/Teacher in the Science of ..possibly Dress making/ Born St Just.
I haven't found a marriage for her either
Areatha GE Marden//grand daughter/ 4/ born Truro.
Neither can I find the birth of this child.
Ambers