Mary Maxwell

I'm researching great grandmother Mary Maxwell who came to Adelaide South Australia on the "Elgin" as an orphan girl in 1849, aged 14, although her marriage age & death age would have had her born in 1838, so therefore only 11. Have been unable to locate any information other than her husband, William Pritchard, stating in her obituary that she was from Dublin. Can anyone help with how to access Orphanage records which may give me some insight into her parents etc.