The problem is Eliza's parents
Eliza was born in 1847 in Gravesend to Mary Lyon. I have the birth certificate.
Did Mary register the birth?
What was her occupation?
What address was on the b/c?
Might be of some help with the finding Mary on 1841/1851
There is a Mary Constant age 20 Dartford Kent servant on 1851 census but noted as U (unmarried)
HO107; Piece: 1587; Folio: 131; Page: 1