The woman, now 81, had lived with the man for 17 years before she moved into a Bundaberg retirement village and he moved into a Gympie nursing home.
The man, who had never married and had no children, died last year, at age 92, without leaving a validly-executed will.
In order to claim his estate, the woman, who now has dementia, had to prove she was still in a de facto relationship with the man for two years prior to his death.
In a decision that has relevance for de facto partners involuntarily separated in old age because of ill health, a Supreme Court judge found there was no evidence that the woman was the man’s spouse.
Justice Ann Lyons ordered letters of administration on intestacy issue to the man’s closest relatives at the time of his death, his niece and nephew, who are now entitled to his entire $1.6 million estate.
Barrister Caite Brewer, for the niece and nephew, said unlike a married spouse, who remained a spouse at law despite losing capacity or having a lengthy separation due to illness or moving to a nursing home, a de facto spouse may not.
Ms Brewer said she believed it was the first estate decision of its kind, addressing issues of lengthy separation of de facto partners due to loss of capacity or illness.
Justice Lyons said it was significant that there was no evidence of any contact by mail, telephone or personal visits between the couple after 2016.

The woman, who was still driving up until 2019 and had travelled long distances, only visited her long-term partner twice between 2013 and 2020, the court heard.
The couple had lived together on his properties, until the widowed mother-of-seven’s health began to decline and she felt she could no longer care for her partner, who had advanced dementia.

“At no time did I consider our relationship to be ended when I moved to the retirement village or when (the man) had to move to Gympie to live in a nursing home,’’ the woman said in a statutory declaration.
She said if the man had not had dementia and she had been capable of continuing to care for him at home they would still be living together.
Justice Lyons said although one person in a relationship had lost capacity and the ability to communicate meaningfully, the other party could still show commitment to the relationship.
“This is shown in a myriad of ways every day in nursing homes, hospitals and retirement villages and family homes in our community,’’ Justice Lyons said.
It was shown by providing care as well as by visits, letters, cards, flowers and gifts.
Justice Lyons said the woman did not nurture or maintain the relationship in any way.
A 2010 letter found among the man’s personal papers after his death, in which he said he wanted to leave a property to his then partner, was not a valid will.
The woman last year rejected an offer to settle proceedings, which, if accepted, would have seen her receive a $350,000 property.