In recent months, Cook's health took a turn for the worse. She was forced into hospital for two months where she staved off pneumonia and breathing problems.
"The nurses and doctors told her that it would be a miracle if she lived past the holidays, so the fact that she's still thriving is just a really great thing," Salvatore said.
Despite the odds, Cook persevered, but she was told by doctors she couldn't return to her apartment without 24-hour care - an expense her health insurance would not cover.
Cook, who is childless, has no close family in California and had lived in her complex for 30 years.
Desperate not to lose his friend, Salvatore turned to the internet for help. He started a GoFundMe page and within five hours had raised enough money for Cook's care. After a month, he had raised AU$66,000 ($68,000).
However, despite the generosity of strangers, trialling caretakers proved costly and the donated funds were quickly depleted, so Salvatore invited Cook, and her beloved pet cat Hermes, to live with him.
Cook said yes.
"She couldn't be happier that I asked," he said. "I was over there visiting most days anyway.
"The only other option was for her to go into a facility. I just couldn't do that to someone who is like my own grandmother.
"She's doing great. If you could see her right now, she looks so cute on the couch with her feet propped up. She just hangs out on my couch and watches TV."
The two have quickly settled into a routine, Cook told Today: "He cooks for me.
"If he can't make it as an actor, he can make it as a chef," she said.
"We always watch the news," she added. "We mostly talk and drink Champagne and eat peanuts."
Their fast friendship was forged with Champagne.
After months of salutations through their respective kitchen windows, Salvatore knocked on Cook's front door.
"She offered me a glass of Champagne - it's her favourite drink - and we just sat down and talked," he said.
"We connected right away. Back when she was a young adult, she had a lot of friends who were gay, and I'm also gay, so I think it made her feel safe at home and at peace to sort of have that bond again."
It's a bond that Salvatore is grateful for.
"My life has changed forever because of Norma and what happened. It gave me hope again. I'm forever grateful for Norma because I feel like I'll carry this with me for the rest of my life," he wrote on his GoFundMe page.
Faith in humanity restored.
Salvatore frequently posts photos of their adventures on social media with the hashtag #myneighbornorma.
