My feeling is this...
Isabella was their first child, and she was born where ever, and baptised in a Protestant Church, in Woolwich.
The mother was Irish (Bridget Cleary) and I assume Catholic. the father was Scottish, and Presbyterian.
At some point, they went back to Ireland...(after 1850, but before 1855). Where they went on to have more children...one in 1855, baptised in RC church, then another in 1857, also baptised in an RC church. Three months after the second child is baptised, Isabella is as well. Maybe as a young girl, she asked to be abptised in the same church...maybe the irish side of the family was putting pressure on the mother...maybe the Church requested she be baptised, as she was later to be "Sponsor" to one of her younger sisters.
I'm my feelings/thoughts way out?