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Olivia Newton-John is urging fans to donate to a cancer facility in her native Australia in memory of her sister, who lost her fight against the disease last week.

The "Grease" star's sibling, Rona, was diagnosed with brain cancer earlier this year, and the singer/actress called off her Las Vegas residency to spend time with her.

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Rona passed away on Friday at the age of 70, and Newton-John has shared her grief with fans in a post on her website.

She writes, "My beautiful sister Rona sadly passed on May 24th in Los Angeles. It was May 25th in Australia -- which was our mother Irene's birthday. Rona died of a very aggressive brain tumor and mercifully suffered no pain."

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"She was surrounded by the love of her four children -- Fiona, Brett, Tottie and Emerson and, her wonderful friends. I will miss her forever -- my beautiful, smart, talented, funny, brave sister Rona."

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Newton-John has requested fans avoid sending flowers to mark Rona's passing and instead donate to the Olivia Newton-John Cancer and Wellness Centre at the Austin Hospital in Melbourne, where a new program will be created in her sister's memory.

She adds, "In lieu of flowers the family would appreciate donations to the Olivia Newton-John Cancer and Wellness Centre where a brain tumor wellness program will be started in her name. Thank you all for your kind words of love and support."

The 64-year-old entertainer, a breast cancer survivor, helped launch the multi-million dollar center last year.