This is Frances in
1861 - Clergyman's Widow, born Tissington.
RG9; Piece: 2521; Folio: 41; Page: 26 Ashbourne, Church Street.Not sure where the kids were, or who the others present are - a Niece and a Servant ....
Robert snr died in Camberell, about a year before the 1851 census, so as you found Robert Jnr with his Gran, I'd guess the girls are with Mum - somewhere ....., but none of them are using their understood PoBs in the 1851 it seems ....

Frances died on 15th April 1884: Her £650 14s Will was proved June 1884, Ashbourne by her son the Rev. Robert Feyrer of 'Therfield', Southwood Lane Highgate and Mary E Law, wife of Channell Law Esq, of 36, Outram Road, Croydon