Using Brian Lawson's census index as a starting point I looked at the following Ellen Kneales in Andreas in 1861:

RG9/4410 f.20. p2
Balla~~na Quarterland, Andreas (dist 2)
Thomas Kneale - mar - 65 - Tailor - Andreas
Jane Kneale - w - m - 58 - Andreas
Ellen J Kneale - d - 14 - Andreas

RG9/4410 f.14 p.21
Andreas Village? (very hard to read)
James Renshall - h - m - 52 - Annuitant - England
Ann Renshall w - m - 46 - Bride
Ellen Kneale - wife's daughter - 18 - Bride

[Familysearch: James Renshall mar. Ann Kneale 29 Jan 1857 Bride IGI ext]

Also, on p.22 was
Ballavastan?, Andreas
John Kneale - h - wid - 67 - Ag lab - Andreas
Ellen Kneale - sister - 39 - lab - Andreas
(but there may be no connection.)

RG9/4410 f.57 p.12 sch.58
Ballasair? Andreas
Philip Teare household:
Ellen Kneale - maid servant - un - 20 - Andreas

Regarding birthplaces given on census records - if the parents are giving the information they are likely to say where the children were born. When the children grow up and answer for themselves, when asked where they come from, might answer with where they grew up or last lived. Just a thought.