Hi DDRAIG
Although this on the Northumberland Board Berwick is actually in Scotland. The 1851 Census states she was bc.1846 (not 1848). I note the birthplace given for her sister is Bridgeston but can't find such a place - wonder if it should be Bridgeton which is a district of Glasgow i.e. both girls born Scotland but then it's maybe a district in Northumberland.
Isabella's surname suggested a Catholic connection - can find no trace of a marriage for her and Charles Ward although the 1851 census states that she, like him, born Gloucestershsire. Couldn't find them in 1861.
Anyway, as Scotlands People have recently added some Catholic Records to their site I checked on there and think I could have found Catherine's baptism in Glasgow. (I note her father was a Rail Labourer so no doubt they moved around a lot - the baptism is 3 months after the birth so they may well have moved from Berwick to Glasgow by then). The details are:
Catherine Ward b.31/8/1845, bp.27/10/1845 St. Andrews Catholic Church, Glasgow, dau. of Charles Ward and Isabella McConnell . Checked the 1851 Census for Scotland and couldn't find another Charles and Isabella there nor a Catherine Ward.
As your Catherine aged 5 in 1851 i.e. bc.1845/1846 the above entry fits - looked at the original entry and mother's surname definitely looks like McConnel and not McConnor.
Annette