Rosealie Stuart was married to John Andrew Stuart's brother Daniel in March 1973 when two drums of fuel were thrown into the downstairs foyer of the Fortitude Valley nightclub and set alight.
Her evidence before the Brisbane Coroners Court on Thursday came as lawyers called for former police officer Roger Rogerson, who is behind bars in NSW for murder and was part of the initial investigation into the attack, to be called to testify.
Rogerson is the only person still alive who signed a confession made days after the firebombing by James Richard Finch, Vincent O'Dempsey's lawyer Chris Minnery told the inquest.
He said Rogerson could also be asked about the possibility of any involvement by Sydney-based criminals.
The application was supported by some legal representatives, but counsel assisting Stephen Keim said information like details of a conversation between detectives and Rogerson had already been provided to the court.
Rogerson's lawyer had also instructed that his client would not consent to giving remote evidence.
"We don't think it's an exercise logistically or financially justified," Mr Keim added.
Coroner Terry Ryan is yet to rule on the request.
Ms Stuart, now 78, said her brother-in-law was a liar and bragger who often used a pseudonym because he "had a bad reputation".
At the time a mother-of-four young children, Ms Stuart said days after the fire she overheard John Stuart - who had been questioned by police but not arrested - reassuring Finch that they wouldn't be caught.
John Stuart said police didn't know of the existence of Finch, who had come from the United Kingdom only a few weeks earlier, Ms Stuart told the inquest.
She heard the men talking in raised voices with John Stuart saying he would "take care" of the family if they found out.
In fear for their safety Ms Stuart told her husband, who initially refused to call police on his brother, but agreed when Ms Stuart threatened to do so herself.
John Stuart was arrested that night, but Finch escaped until the following day.
Ms Stuart testified against the men who were convicted of murder in 1973.
Both have since died.
"I've been told to keep my head down to this day because Finch threatened to kill us," she told the inquest.
She said the family was under protection and she couldn't contact her family for years after refusing a police request to move to Canada.
"I was so frightened," she added.
"I was just in this nightmare I couldn't get out of."
The Whiskey inquest was reopened after the firebombing was mentioned in trials in which Vincent O'Dempsey and Garry Dubois were convicted of killing Barbara McCulkin and her two daughters.
The trials heard the killings may have been motivated over fears Ms McCulkin would try to implicate O'Dempsey in the firebombing.
