It appears that Mary's parents also had another daughter by the same name who was born and died 3 years earlier in 1855 (refer NSW BDM birth certificate 3434/1855 V18553434 72 and NSW BDM death certificate 768/1855 V1855768 120). The death certificate here is noted as being "Infant".
It may be possible to confirm family relationships with Mary by comparing test results with other carriers of her mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Mary: