The birth certificate for her daughter Eileen born 13/2/1913 shows the Mothers Surname/maiden name as
Mahoney Margaret, 24years of age,Place of birth Port Fairy,Victoria
so that would make her Birth date 1889 c, it is obvious that she shifted from that area as Eileen {her daughter}was born in
Fitzroy,
Melbourne before being placed in the St
Josephs Foundling Hospital {babies home} in Broadmeadows,
Melbourne around 15/7/1913 some 5 months after birth.
I appreciate that this could be like looking for a needle in a haystack,but one will never know if you don't give it a go !!!