Welcome to Ireland Reaching Out and apologies for the delay in getting back to you.
I don't think that Catherine and Hannah could be one and the same. I would consider that Hannah would have more in common and would be used interchangeably with other names like Anne/Ann/Anna/Nora etc and Catherine with Katherine/Katie/Cathy/Kitty or maybe Kay for example.
There are some gaps in the baptism records for Leighlinbridge between Jan 1783 and Dec 1819. Certainly until you have more to go on I would consider them to be two different people.