Hi,
Trying to think 'outside the square' here, from my armchair....
The NSW BDM online index includes at their Early Church Records, Roman Catholic marriages at Geelong, Vic under the district code of LS, and under the code LR there's Roman Catholic marriages at St Francis, Melbourne....
So, if I search the NSW BDM online index, using the years 1835 - 1855, the district code LR and the keyword cath?rine there's over 50 brides, and at the LS code there's just 2.
Also, I notice from Merlin's post that Henry's surname would seem to have been MIRGAN, as Catherine's nee is recorded as Monaghan on those baptisms #94 - #97. I wonder if the marriage register for St Marys is extant? Perhaps the marriage for Catherine is in that register.
Cheers, JM