The "Grease" star is currently battling breast cancer for the third time, but it was the July (20) passing of Kelly, who quietly suffered from the same ailment, which really pushed her to step up her charitable efforts to support cancer research.
"Kelly was a lovely woman and (it was an) incredibly tragic loss," she told Us Weekly. "It just strengthened my resolve to find an end to cancer."
"Losing friends and losing people that you care about just makes me even more determined to do this research."
Olivia had been friends with Kelly for years, after co-starring in "Grease" with the late actress' husband, John Travolta.
As for her own health crisis, the 72 year old, who was diagnosed with breast cancer in 2017 after battling the illness twice before, is doing "really well" and is trying to remain positive as she relies on marijuana to ease her pain.
She said, "Thanks to my husband (John Easterling) and his plant medicine, I'm doing really well."
"I think it's just keeping a positive attitude and believing that I will be OK. And talking to my body and doing all the things that I can to support myself emotionally and mentally."
Last year after Kelly Preston's death, Olivia Newton-John posted a throwback picture of them together as she remembered her late friend as "A loving, devoted wife, mother and sweet friend." She added, "My heart breaks for John, Ella and Ben. No words can express my sorrow for her family. Kelly's light shines on in her beautiful children."