Olivia Newton-John, the Grammy-winning superstar who reigned on pop, country, adult contemporary and dance charts with such hits as “Physical” and “You’re the One That I Want” and won countless hearts as everyone’s favorite Sandy in the blockbuster film version of “Grease,” has died. She was 73.

Newton-John, a longtime resident of Australia whose sales topped 100 million albums, died Monday at her southern California ranch, John Easterling, her husband, wrote on Instagram and Facebook.

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“Olivia has been a symbol of triumphs and hope for over 30 years sharing her journey with breast cancer,” he wrote. “We ask that everyone please respect the family’s privacy during this very difficult time.”

From 1973-83, Newton-John was among the world’s most popular entertainers. She had 14 top 10 singles just in the U.S., won four Grammys, starred with John Travolta in “Grease” and with Gene Kelly in “Xanadu.” The fast-stepping Travolta-Newton-John duet, “You’re the One That I Want,” was one of the era’s biggest songs and has sold more than 15 million copies.

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“My dearest Olivia, you made all of our lives so much better,” Travolta wrote in an online post. “Your impact was incredible. I love you so much. We will see you down the road and we will all be together again. Yours from the moment I saw you and forever! Your Danny, your John!”

“I worship this woman. My mother. My best friend,” her daughter Chloe Lattanzi wrote.

Robin Roberts, the anchor for ‘Good Morning America’, who was diagnosed with breast cancer in 2007, said, “Very sad news.cGreat admiration for how she bravely faced breast cancer. Condolences to her loving family and friends.”

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“Rest In Peace dearest Olivia,” actor Titus Welliver tweeted.

“Guardians of the Galaxy” filmmaker James Gunn tweeted, “Really sad to hear about the passing of Olivia Newton-John. My first real crush as a kid.”

” I loved Grease & her music & I coincidentally also bought & lived in for a while the wonderful home she built in Malibu. May she Rest In Peace,” he continued.

“Physical,” the bouncy, R-rated smash released in 1981, was No. 1 for 10 weeks and was named Billboard’s song of the year despite being banned by some radio stations. An aerobics-friendly promotional clip, filmed in the early years of MTV, won a Grammy for best video.

Both musically and image-wise, she reinvented herself during those years. The blonde, ever-smiling Newton-John initially favored mild pop-country songs such as “Please Mr. Please” and “Have You Never Been Mellow” and soft-breathing ballads like “I Honestly Love You,” which in 1975 won Grammys for best female pop vocal and record of the year. But she picked up the tempo in “Grease,” especially after Sandy ditched her white sweaters and blouses for waist-high, black leather pants. “Physical” even made Newton-John blush as she told her would-be lover “There’s nothing left to talk about/Unless it’s horizontally” and finally called out “Let’s get animal! Animal!”