I don't know how positive you are about her being born in Dorset, but this would tie up nicely:
1861
RG9/47 65 33
Westminster St John, Middlesex
21 Wilton Street
Ellen Hansford, head, wid, 41, Laundress, b. Suffolk Horwich
George, son, 17, b. Westminster St John
Sarah, dau, 15, scholar, b. do.
Emma, dau, 12, scholar, b. do.
Ellen, dau, 10, sholar, b. do.
Elizabeth, dau, 8, scholar, b. do.
Alfred, son, 5, scholar, b. do.
Richard, son, 3, scholar, b. do.
and going back to 1851
HO107/1479 358 19
Westminster St John the Evangelist
47 Peter? Street
Alfred Hansford, head, 27, Painter, b. Devon
Ellen, wife, 31, Dressmaker, b. Essex
George, son, 6, b. St John the Evangelist
Sarah, dau, 5, b. do.
Emma, dau, 1, b. do
What do you think?