Hi shazzi-b
I think I could be onto something

Sarah is given as her mother,I cound not see a marriage for her on those Wincombe marrage records.
This is the family that I found in 1841 living in Yatton, which is quite close to Winscomb.
107/968/12/14/31/3
James Knowles 62 Cordwainer
Phebe 63
Edward 26 Plasterer
Phebe 21
EMILY 14
Charles 10
Mary 5
As no relationships are given, looking at the ages it would make Phebe about 49 when she had Emily and 58 for Mary, I think that pushing things, so maybe as Sarah was unmarried perhaps these are Emily grandparents

I notice from the 71 census that the eldest child is a son James Knowles Summerall, possibly named after her grandfather.