Sadly, there was never a headstone, Lydart.
It was a common grave in the Borough Cemetery, Cambridge, not paid for by the family (times were 'ard!), and contained four or five other "residents", according to the register in the cemetery office.
I think I've found the grave of Fanny's daughter-in-law in a churchyard in Holywell, near Needingworth. I shall try to contact her family, but I haven't decided on the best way to do this, yet.
'Hat.