Hi Frances,
I got Catherine Christians exact birthdate from information my grandfather gathered. When he died, I took over the all of the notes he and his father gathered over the years. I'm not sure how they got separated from the source documents that they had, but those went to another cousin, who threw them away. (It makes me sick just to type that.) I think that I have found Catherine in the Isle of Man Census for 1841

CHRISTIAN, Catherine 2years Andreas Piece:1463/1 Folio 39 page 13

also on that page is...

CHRISTIAN, Elizabeth 30years Andreas Piece:1463/1 Folio 39 page 13

and on another page that is listed alone but shows on the census next to Cathrine and Elizabeth I found...

CHRISTIAN, John 45years Andreas Piece:1463/1 Folio 38 page 12

Then in the Isle of Man Census 1851 I found...

CHRISTIAN, Catherine E. 13yrs Andreas Piece:2524 Folio 43 page 17
CHRISTIAN, Charlotte E. 10 months Andreas Piece:2524 Folio 43 page 17
CHRISTIAN John M. 53yrs Andreas Piece:2524 Folio 43 page 17

Then in the Isle of Man Census 1851 I found...

CHRISTIAN Catherine 21yrs Andreas Piece:4410 Folio:10 Schedule:45
CHRISTIAN Elizabeth 59yrs Andreas Piece:4410 Folio:10 Schedule:45

I don't know for sure that these are all the correct Catherine Christian, or even the same Catherine Christian, but the people who are listed with her seem to match my information.

I hope that helps.
Thanks,
Tracy : )