The shipping record says that Catherine who arrived in Dec 1884 was from Meath, Ireland.
The only 1888 NSW marriage that fits is this one in Sydney:
2/1888 GRAHAM GEORGE MORGAN CATHERINE A SYDNEY
There is a St Michael's Cof E in Woollahra suburb of Sydney.
However, it seems according to one tree that the Catherine Ann MORGAN who married George GRAHAM was born in NSW to parents John MORGAN & Catherine FINNEMORE.
Birth 5015/1860 MORGAN CATHERINE A JOHN CATHERINE BATHURST
EDIT: It's possible the author of that tree couldn't find Catherine in shipping records and found one born in NSW to complete the tree. I know some are satisfied if the tree is complete regardless of its accuracy.