Mary was born in Tipperary, Ireland in 1847 according to her death certificate, but that would have made her 12 at the time of her marriage in 1859. Her age upon arrival in Queensland in 1880 was stated as 40.
I believe that her birth date to be in c1840.

Death: Qld Death Cert No. 1888/C003819. states that, in 1888, Mary HEALY (nee Dwyer) died in Queensland. Her father was Michael DWYER who was a farmer and her mother's name was not recorded.

Qld Death Cert No. for...
Mary Healy
Event date: 09/08/1888
Event type: Death registration
Registration details: 1888/C/3819
Mother: -
Father/parent: Michael Dwyer

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Published in…
The Brisbane Courier, Saturday 8 September 1888
“In the SUPREME COURT of QUEENSLAND
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ECCLESIASTICAI, JURISDICTION.
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In the GOODS of MARY DWYER HEALY, the Wife of John Healy, of Rockhampton, in the Colony of Queensland, Labourer, Deceased.
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Notice is hereby given that, after the expiration of fourteen days from the publication hereof, application will be made to the said Honourable
Court that LETTERS of ADMINISTRATION of all the goods, chattels, credits, and effects of the abovenamed Mary Dwyer Healy, deceased,
who died intestate, may be granted to the above-named JOHN HEALY, of Rockhampton afore-said. Labourer, the Husband of the said deceased.
Dated at Rockhampton this Twenty-ninth day of August. 1888.
WALTER THOMPSON, Proctor for the said John Healy, Rockhampton. By his Agent - L. F. BERNAYS, Proctor, George-street, Brisbane.”
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South Rockhampton Cemetery record...
Mary HEALY sex-F aged-41 burial-Friday, 10 August 1888 area-RC Section-33 Grave No.-1560 occupation-Housewife