Olivia Newton-John on Kelly Preston's 'Private' Battle With Breast Cancer (Exclusive)

The actress also opened up on how John Travolta has been healing in the wake of his wife's death.

Olivia Newton-John is opening up about Kelly Preston's private battle with breast cancer, and how the late actress' family is healing. Speaking with ET's Rachel Smith, the actress and singer reflected on what she missed most about Preston.

"She was a very a beautiful person, inside and out, and was beautiful to look at," she said of Preston -- who was married to Newton-John's close friend, John Travolta, for nearly 29 years. "But she had a gentle spirit and I just feel so, so much for John and the children. It's hard to put into words."

Preston died on July 12, at the age of 57, after a two-year battle with breast cancer that she'd kept out of the public eye. The news was a shock to the world, and Newton-John said the family has been "coping as well as you can imagine."

"Loss is loss, and to lose your mother and your wife is an incredibly difficult thing, and it takes a long time," she shared. "But ultimately it's a private journey and I respect that for them."

While she said that she doesn't speak to Travolta on a daily basis, Newton-John shared, "We are in contact and I send my love and support as often as I can."

The 72-year-old entertainment icon was first diagnosed with breast cancer in 1992. However, unlike Preston -- who kept her battle largely private -- Newton-John was forced to go public with her own diagnosis.

"There was going to be an article released in one of the gossip papers that I was dying of cancer," the actress recalled. "When I heard that, I decided that rather than frighten my family and my friends, it would be better to just come out with it."

She has since been very public and candid about her struggle with breast cancer, as her affliction has gone into remission and reemerged multiple times over the decades. Now, she's feeling strong, determined and dedicated to helping others.

The entertainer -- who lives with her husband, John Easterling, on their ranch in Santa Barbara, California -- recently announced the formation of the Olivia Newton-John Foundation.

"I'm so excited. This has been something that's been in my heart and my mind for many years," she said of the new organization, which is focused on finding new avenues for cancer treatment and recovery that are gentler on a person's body.

"Being a cancer thriver of 28 years and having gone through surgery and chemotherapy and radiation I always had this dream that we could find kinder ways of treating cancer," she added.

See more on the Olivia Newton-John Foundation and their efforts here.