Hi Katherine,
Here is the birth :
Digger - South Australian Births 1842-1906 (c) SAGHS

Surname: CONDON
Given Names: Mary
Date: 1854-05-11
Sex: F
Father: Enoch CONDON
Mother: Emma KAMBER
Birth Place/Residence: Bowden
District Code: Ade
Symbol:
Book: 4
Page: 338
Cross Reference:

Can't see a marriage in SA.
Can't see a marriage I can be sure of in VIC there are a couple with no birthplace given which might fit.

There are theses 3 deaths which fit the age. I can't see births for any of them, but clutching at straws a bit :(
Digger - Death Index. Victoria 1921-1985

Surname: QUINTON
Given Names: Mary Agnes
Father: Unknown
Mother: Unknown UNKNOWN
Death Place: SUNBURY
Age: 81
Age Code:
Year: 1934
Reg Number: 15174
Event: D

Surname: RIPPINGALL
Given Names: Mary Ann
Father: Unknown
Mother: Ann BROWN
Death Place: CHAM
Age: 81
Age Code:
Year: 1934
Reg Number: 2018
Event: D

Surname: DICKENS
Given Names: Mary Ann
Father: Unknown
Mother: Ann BROWN
Death Place: CHAM
Age: 81
Age Code:
Year: 1934
Reg Number: 2018
Event: D

You seem to have a very accurate date of death. Where did you get that information ? Do you know where in Melbourne ?

Regards
Alison