The pair were on their first big holiday together from Victoria when they made a visit to Tasmania's picturesque Port Arthur on April 28, 1996.
When a lone gunman opened fire, Ms Loughton did her best to protect the 15-year-old.
"I gave birth to my daughter and I lay on top of her when she took her last breath," she said.
Sarah was one of 35 people murdered in what remains Australia's worst mass shooting in modern history.
Ms Loughton was shot in the back, forcing doctors into a marathon procedure and the removal of her left fibula and half of her hip to use as bone grafts.
Her attendance at Tuesday's 30th commemoration at the historic site is the first time she has been to Port Arthur since 1997.
"I just turned 70. I realised if I don't go there soon, I'll be 80 or dead. I have to go back and lay some flowers," she said.
"When you lose your children, you lose your future. It is the continual loss of what could have been for her and for me."
Quiet reflection and words from survivor Jane Scholefield, who hid behind a wall in the penitentiary building to avoid the shooting, will form part of the ceremony.
A minute of silence will be held at 1.30pm, the moment the gunman entered the Broad Arrow Cafe and killed 12 people.
The tragedy, in which some two dozen people were also injured, prompted gun law changes and a buyback scheme that led to the destruction of more than 640,000 weapons.
Gun reform has been under a recent microscope since 15 people were killed in a shooting targeting the Jewish community at Bondi in December.
"The shootings ... just five months ago, showed that there are still rapid-fire guns in the hands of the community," Ms Loughton said.
"These guns must be put out of reach for the safety of all."
Ms Loughton and Gun Control Australia's Roland Browne said they supported Prime Minister Anthony Albanese's proposed cap on the number of guns a person can own
"The lessons from the late '80s and early '90s remain," Mr Browne said.
"Work still needs to be done and our group will continue to do it."
Tasman Council deputy mayor Maria Stacey, who was at the site on April 28, 1996, said anniversaries brought out a mix of emotions.
The demographic of the peninsula, which is home to a few thousand people, was changing with time, she said.
"(But) it's quietly there, the whole tragic event is always just under the surface," Ms Stacey said.
Mr Albanese thanked Walter Mikac, who lost his wife Nanette and daughters Alannah and Madeline in the shooting, for leading the call for gun reform in 1996.
"Australia is a better place because the government and the parliament of the day came together to answer Walter's call," he said.
"This is what we hold on to - the abiding memory that somehow amid the most terrible darkness the best of humanity found a way to shine."
Tasmania's Premier Jeremy Rockliff said the state would never forget the lives lost and every person whose life changed forever.
Gunman Martin Bryant, who is now aged 58, is serving 35 life sentences and will never be released from Risdon Prison in Hobart.
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