"The news of Kirstie Alley's passing is very sad," Remini, 52, said in a statement shared with Rolling Stone.
The actresses had been engaged in a years-long public war of words after Remini broke with the Scientology in 2013. Alley was very critical of the King of Queens alum's claims about the Church, even calling her former friend a "bigot" in a 2013 Howard Stern interview.
In her statement this week, Remini added that she's thinking of the Cheers star's children, True Stevenson, 30, and Lillie Stevenson, 28, during this time.
"Although Scientologists don't believe in prayers, my prayers do go out to her two children, who are now without their mom," she continued. "I hope they can, one day, free themselves of this dangerous and toxic organization."
On Monday, Alley's children confirmed her passing "after a battle with cancer, only recently discovered." She was 71.
"She was surrounded by her closest family and fought with great strength, leaving us with a certainty of her never-ending joy of living and whatever adventures lie ahead," they said in a joint statement to PEOPLE, which was also shared on Alley's Instagram page. "As iconic as she was on screen, she was an even more amazing mother and grandmother. We are grateful to the incredible team of doctors and nurses at the Moffitt Cancer Center for their care."
Cindy Ord/Getty Kirstie Alley
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True and Lillie continued, "Our mother's zest and passion for life, her children, grandchildren and her many animals, not to mention her eternal joy of creating, were unparalleled and leave us inspired to live life to the fullest just as she did. We thank you for your love and prayers and ask that you respect our privacy at this difficult time."