Registration of Births Deaths and Marriages commenced mid 1842 so Lucy's birth if 1841 would not be registered.Rarely, a registration of a birth prior that year is made later when a sibling is born.I could not find any entry for Lucy.
I did a search for her marriage to Thomas Knight by various ways and no luck.However, there is a marriage on 29 Mar 1890 - Robert Pointon age 34 to Lucy Higman age 40 (she is listed as a widow)at the Res of Thomas Barker, Wokurna.Lucy's father is listed as John Higman. That would make Lucy born 1850??Maybe another Lucy.
I did find two children for Thomas Knight and Lucy Higman they were Ephraim born 25 July 1876 Adelaideand Martha born 15 Oct 1878, Thebarton.
I could not find a death for Thomas Knight. Except a Thomas Skinner Knight died 6 Sept 1869 age 36at his residence Reedy Creek District TAL
There was also a child born Edith May Anderson born 29 Mar 1886 to Lucy Higman and William Anderson Teal Flat District TAL.
Sorry, this doesn't really answer your question but probably makes it more confusing!
There were a few other Higman's around the place.One was Richard Higman married Caroline Swann 4.4.1867, Mount Pleasant District TAL.Richards father is James Higman