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Sinead O'Connor isn't letting Miley Cyrus off the hook so fast. 

On Monday, she posted her fifth open letter to the 20-year-old, demanding an apology for her tweets, which seemed to poke fun at Sinead's mental health issues several years ago. 

Miley addressed the ongoing back-and-forth during her appearance on the "Today" show last week, telling Matt Lauer that she's a "big fan" of Sinead's and that "it's all good." 

Apparently, that wasn't enough to squash the beef.  In her new letter, Sinead urges Miley to publicly apologize for her tweets, which she writes "contributes to the silences with allow suicide to flourish." 

Sinead adds that "people die every day because of the type of thing you did" and that apologizing "will save lives." 

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