Jackie, who sold more than 500 million novels in more than 40 countries in her four decades-long career as a writer in raunchy female fiction, died of breast cancer. She was 77.
Despite being diagnosed six-and-a-half years ago the British author, who lived in Beverley Hills, told few people about her illness, saying she did not want to “burden” others with it.
Dame Joan, who only found out in the last fortnight, posted a picture online of herself and Jackie, writing: “Farewell to my beautiful brave baby sister. I will love you and miss you forever. Rest in peace.”
The pair, who had been rumoured at times to have a difficult relationship, were pictured together in London just a few days ago while Jackie was on a promotional tour for her new novel The Santangelos.
Dame Joan tweeted: “Lovely evening @thewolseley before sis went back to LaLaLand.”
Jackie’s publicist Melody Korenbrot said the author, a mother-of-three and grandmother-of-six died on Saturday in Los Angeles.
Paying tribute, her family said she had broken new ground for female writers in fiction.
“It is with tremendous sadness that we announce the death of our beautiful, dynamic and one of a kind mother, Jackie Collins, who died of breast cancer today,” they said in a statement.
“She lived a wonderfully full life and was adored by her family, friends and the millions of readers who she has been entertaining for over four decades.
“She was a true inspiration, a trail blazer for women in fiction and a creative force. She will live on through her characters but we already miss her beyond words.”
Her novels, telling stories of glamour, sex and affairs in Hollywood, include The World Is Full of Married Men, The Love Killers and The World Is Full of Divorced Women.
Her title Hollywood Wives became a New York Times best seller and was made into a television series starring Farrah Fawcett and Anthony Hopkins.
Jackie, who was made an OBE in 2013, spoke to People magazine six days ago for what would be her last interview.
She said she had no regrets about keeping the news of her illness private.
“I did it my way, as Frank Sinatra would say,” she said. “I’ve written five books since the diagnosis, I’ve lived my life, I’ve travelled all over the world, I have not turned down book tours and no one has ever known until now when I feel as though I should come out with it.”
In an interview with the Press Association earlier this month Jackie said she chose to celebrate life rather than mourn those close to her who had died.
“I refuse to mourn people, because everybody dies. Death and taxes, you can’t avoid either,” she said.
Her mother Elsa Collins, second husband Oscar Lerman and fiance Frank Calcagnini all died from cancer.
Oprah Winfrey, Bond star Sir Roger Moore and television personality Sharon Osbourne are among those who have paid tribute to the novelist.
Private memorial services will be held for family in America and the UK, and those wishing to make donations can do so to the Susan G Komen Breast Cancer Organisation in America and Penny Brohn Cancer Care in the UK.