Using Ancestry records this is what I see for Honora McGRATH, arriving "Corona", 1879, Sydney -
All New South Wales, Australia, Assisted Immigrant Passenger Lists, 1828-1896 
https://www.ancestry.com.au/search/collections/1204/Name:                           MACGRATH Honora   20 years
Native Place:                  Limerick
Parents names, and , if alive, their residence:   Limerick  **** WILSON   (might be Eliza)
Religious denomination:  RC
Read Write:                    both 
Relations in the Colony:   none  
Name:                           ENGLISH Johanna   20 years
Native Place:                  Limerick
Parents names, and , if alive, their residence:   Michael & **** Limerick
Religious denomination:  RC
Read Write:                    both 
Relations in the Colony:   John CONWAY   cousin      
New South Wales, Australia, Immigration Deposit Journals, 1853-1900
https://www.ancestry.com.au/search/collections/2000/Name of Depositor:  John CONWAY
Deposit paid:           3 Dec 1878
Person for whom remittance is made: 
                                             Residence             Name & address of referee
ENGLISH Johanna   19 years    Ballinagrana           Thomas FITZGERALD
McGRATH Honora    21 years    Kaldronin
                                              Ireland   
At 1879 and arriving "Corona"    Honora McGRATH has no relatives in the colony.
From the obituary for Patrick McGRATH, died 1932...he is 86 years old and arrived at age 23 years  ......arrived ~ 1869.   
New South Wales, Australia, Immigration Deposit Journals, 1853-1900
Apart from finding names on the NSW BDM index what documents do you have for BDM?