The Grease star, whose daughter Chloe Lattanzi starred on Dancing With The Stars this year, then revealed she immediately booked an appointment with her doctor and agreed to get a surgical biopsy. She later found out that it was breast cancer.
"All this was overwhelming. It was a feeling of dread, terror, the unknown," Olivia confessed.
"I made the decision that I would be okay. I had to believe I was going to be okay, that my daughter was the most important thing in my life and I would be okay for her."
Olivia has tried numerous therapies such as meditation, acupuncture and medicinal cannabis - the latter of which her plant medicine researcher husband John Easterling grows at their California home.
"I have seen the incredible beauty of the plants and their healing abilities. If I hadn't had that experience, I wouldn't be sitting here talking to you about kinder therapies... your body wants to heal itself. That's why I'm excited to start this foundation."
Olivia was first diagnosed with cancer 1992 and then again in 2013 and 2017.
Despite battling stage four metastatic breast cancer, Olivia revealed in January this year that her tumours had shrunk in size, which she called "pretty amazing," The Sunday Telegraph reported.
"If I hadn't had the experience I'm having with cannabis I wouldn't be able to talk about it," she told the publication.
She also said: “I’d love patients in Australia to have the capability of getting it when they need it.
“Hopefully those studies will help with the government that seems to be a long way behind the rest of the world, well at least America."
Back in April, the singer and actress urged her fans and followers to make their own masks as the global coronavirus pandemic raged.
"We don't need [hospital grade] masks, because health workers need them desperately and there aren't enough for the general public too!" she captioned a photo of herself in a homemade leopard-print face mask.
"Please pass this video on - let's be creative and make our own, like the Czech Republic."
She finished the post by thanking startup Masks 4 All for pushing their critical message to the world.