Olivia Newton-John has remembered Kelly Preston as a ''radiant, warm and gentle spirit''.

The 71-year-old actress admitted her ''heart breaks'' for her 'Grease' co-star John Travolta after his wife tragically passed away on Sunday (12.07.20) after losing her private two-year battle with breast cancer at the age of 57.

In a statement to PEOPLE, Olivia said: ''Kelly was a radiant, warm and gentle spirit -- a loving, devoted wife, mother and sweet friend.

''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.''

Meanwhile, Kelly's 'Jerry Maguire' director Cameron Crowe described her as ''one of the best-kept acting secrets'' before she was cast in the role of Avery, the fiancee of Tom Cruise's character Jerry.

He said: ''Her silent moments are as good as the flashy stuff.

''I'm just sorry that I hadn't seen her recently because I wanted to tell how much I've started to hear from people who said, 'You know ... I watched 'Jerry Maguire' the other night, and I didn't realize how much I wished there was a whole Avery Bishop movie ...' She is missed.''

Jerry O'connell - who played quarterback Frank 'Cush' Cushman in the film - also remembered his late co-star.

He said: ''We had a big rehearsal the first day of 'Jerry Maguire'. It was a pretty star-filled room. I had A HUGE CRUSH on Kelly... No joke, since 'Twins'... Like, IN LOVE.

''Meeting Kelly was maybe the biggest moment of my 21-year-old life, at the time. Kelly must have sensed my apprehension because she was SUPER KIND to me. An angel! Truly.''

Following the news of Kelly's death, her husband John honoured his ''beautiful wife'' - who is also survived by kids Ella, 20, and eight-year-old Benjamin - with a heartfelt Instagram tribute.

Alongside a picture of his late wife, he wrote: ''It is with a very heavy heart that I inform you that my beautiful wife Kelly has lost her two-year battle with breast cancer. She fought a courageous fight with the love and support of so many.

''My family and I will forever be grateful to her doctors and nurses at MD Anderson Cancer Center, all the medical centers that have helped, as well as her many friends and loved ones who have been by her side.

''Kelly's love and life will always be remembered. I will be taking some time to be there for my children who have lost their mother, so forgive me in advance if you don't hear from us for a while. But please know that I will feel your outpouring of love in the weeks and months ahead as we heal.

''All my love, JT (sic)''