Hi David,
Re the Dublin 1792 baptism, the index doesn't show any details for her parentage, and I don't have any euros to gain access to view the record...
Re Rev Youl .... He was in VDL in 1821, baptising children of the military .... eg
At St Johns, Launceston in Nov 1821 baptising Pte Richard Wayne's daughter,
And in June 1821 (but no church or place named) he baptised a John James SMITH, son of a Pte Thomas Smith...
(both events attributed by Clem Sargent as performed by Youl ... page 87 of the book I have cited several times on the threads)
Also, on page 61 of that same book .... Cimitiere had instructions from Macquarie to erect buildings urgently, even if that meant withdrawing convict labour from their assignments .... so the first building at George Town was for the Rev John Youl .... and the next was for the commandant (Cimitiere) ... I think that would place Youl in VDL on frequent basis from early 1818 to post 1821, and thus perhaps his servant (Miss Catherine Brennan) would travel too ... (with perhaps a basin for a kitchen sink

)
Cheers, JM