Hello Cas
I was looking at a few options but have met a few dead ends. I initially thought the other Census may help and as much of Cornwall is on FreeCen
http://freecen.rootsweb.com/you may find what you wanted there. On searching, however
In 1851 there are about 4 possibles with the exact name of Ann Bray (& possibly others Annie or Anne etc). One of the Ann's had a mother with the name of Jane so if I had to guess, I thought she may be a possible.
My next thought was to hope they were married in 1871 & perhaps living in England so we would get a birth location within Cornwall. But I couldn't find an Ann Flynn in 1871 born Cornwall. Given the babe was born in 1878 she probably didn't marry too long before this date.
I then looked for the family in 1891 and found Ellen Jane working as a servant, a possible Thomas living as a boarder and specifying he is single & no sign of Ann.
Do you know when she died. If you had a death certificate would it provide the names of her parents?
Or when she married? Her father's name should be on the marriage record. Parent names would help identify the correct census entry.
Apart from FreeCen, I have found this site very good for Cornwall
http://www.cornwall-opc.org/index.htmbut you will need to find the location of the birth for much benefit.
If you want the detail anything I found, let me know
Trish