"I told her all the things I needed to say.
"She was leaving us... but I could feel like she got it."
Goldsmith said Newton-John "really went down in the past five or six days".
"It wasn't just the cancer that got her, it was other complications, being in a hospital and with a very susceptible immune system.
"She got secondary infections. She's really struggled with a lot of pain."
Goldsmith added that her aunt was "really skinny and really unwell", but was brave until the end.
Newton-John told her niece that she was "not afraid" of death, adding: "I've done more in my life than I could have ever imagined."
Goldsmith said her family would accept the offer of a state funeral from Victoria premier Daniel Andrews.
In May 2017, and after 25 years in remission, Newton-John said her cancer had returned, and confirmed in September 2018 that she was battling it for the third time.
As her health worsened in recent years, Newton-John largely retreated from public and was seen just a handful of times over the past year.
The last time fans saw her speaking on camera was when she posted a Christmas message to her Instagram followers on Christmas Day, 2021.
"I just wanted to take this opportunity to wish all a primarily healthy, happy, peaceful Christmas," she said, looking somewhat more frail than fans were used to seeing her, but still in good spirits. "I want to thank you all for all of your support over the years and I wish you all the best and send you love and light."
Her last TV appearance came a few months before that, in October of 2021, when she made a guest appearance on Dancing With The Stars for the show's Grease-themed night. In honour of the night, Sandy herself, Olivia Newton-John.
As contestants paid tribute to her and John Travolta's iconic 1978 film, Newton-John appeared via a video message to wish them well.
"I'm so thrilled and honoured that you're celebrating Grease tonight! I know your couples have been working really hard and I can't wait to see their performances!" she said.
Newton-John's Instagram account was, in recent years, mostly dedicated to flashback posts from throughout her career and competitions to keep fans engaged with her work.
But, on April 18 this year, came a rare, candid photo – and perhaps the last picture fans will have of her.
"Wishing everyone a Happy Easter on this beautiful Spring day!" she captioned the photo, which showed her smiling happily, dressed casually, and surrounded by a garden of blooming sunflowers.
As "final photos" go, it couldn't be more perfect – an image that summed up everything fans loved about this sunny, supremely talented but always down-to-earth star.
In October last year, Newton-John revealed that she was battling Stage 4 breast cancer but was managing the pain with medical marijuana.
And on Monday, she died at her Southern Californian ranch, surrounded by loved ones, including her husband, John Easterling, and daughter, Chloe Lattanzi.
Easterling confirmed the heartbreaking news in a Facebook post, describing his late wife as "a symbol of triumphs and hope".
"Olivia has been a symbol of triumphs and hope for over 30 years sharing her journey with breast cancer," he wrote.
"Her healing inspiration and pioneering experience with plant medicine continues with the Olivia Newton-John Foundation Fund, dedicated to researching plant medicine and cancer. In lieu of flowers, the family asks that any donations be made in her memory to the Olivia Newton-John Foundation Fund."
