Florence is in the 1871 Census too:-
Church Street, Docking
Robert Bennett; head; married; aged 52; Blacksmith; born Snettisham, Norfolk
Frances Bennett; wife; married; aged 49; born Docking, Norfolk
John I Bennett; son; unmarried; aged 15; Blacksmith Apprentice; born Docking, Norfolk
Florance A Branch; Grand daughter; unmarried; aged 7; scholar; born March, Cambridgeshire
RG10/1858 folio 40 page 5
As she is not shown as a visitor or boarder etc it seems likely that she was lving with them and raises the prospect that either or both parents were dead by 1871.
I checked for deaths in Cambridgeshire, assuming that Florence is indeed the daughter of William and Mary, and found an entry in the index for a Mary Branch aged 26 in the March quarter of 1871 for Cambridge Volume 3b page 355.
I could not find any likely candidate for Mary Ann Branch in 1871 anywhere and whilst there are a few Williams around it is difficult to know whether any of them are prospective "hits" unless you happen to knwo where he was born?
FreeBMD shows only one marriage for a William Branch between 1861 and 1871 in June Quarter of 1867 Norwich Volume 4b page 277. Of course FreeBMD isn't complete but thought you might like to know.
If you've got anything more to go on I'll gladly take another look.
Paul