Have you thought that since she was older than her husband she might have knocked a year or two off her age?
There is an Ellen aged 4 with parents John and Ann on the 1851 census, although it's true that they are in Chorley lodging with Ann's parents, the Blacklidges.
Still there in 1861 though John Kilshaw has died.
Page Number 14
Registration Number HO107
Piece/Folio 2263 / 247