According to FreeBMD, the maiden name of Susans mother was Clark. Also from FreeBMD, there is a James William Eatherton marrying a Susan Clark in 1905 in West Ham....almost certainly these are the parents of your Susan. From FreeBMD i saw that there was also a Thomas Eatherton, born in 1920 - mothers maiden name Clark - in West Ham...again almost certainly Susans brother. From Genes Reunited i noticed an Anthony Eatherton who has Thomas in his line. He also has a James William Eatherton in his line..so from these deductions we can assume that Susans father was James William Eatherton, born in 1964 in Stepney.
James's father was a Daniel Eatherton, born in 1838 - also in Stepney. Daneil's father was a James Eatherton born in Whitacre, Essex in approx. 1808. Thats as far as i can go back with this line. I believe all Eathertons in UK are stemming from this one common ancestory. It could also be (but would require DNA proof) that there is a link between these Essex Eathertons and the Essex Ethertons ( note different spelling).
Hope this helps