Miley Cyrus has compared Sinead O'Connor to Amanda Bynes. The starlet hasn't responded well to the open letter the Irish hitmaker penned this morning, in which she warned Miley her provocative behavior and scantily-clad performances would leave her "prostituted" by the music business.

The former Hannah Montana star has taken to Twitter to slam Sinead, poking fun of her mental health and likening her to troubled actress Amanda, who has spent the summer in a psychiatric hospital. "Before Amanda Bynes.... There was...," she wrote, attaching a screenshot of a tweets from an account she believed was Sinead's, clamoring for psychiatric help. While the account was a fake, Sinead did post suicidal tweets in 2011 and has struggled with mental illness in the past.

Miley also shared a photo of Sinead's 1992 controversial Saturday Night Live appearance, when she ripped up a picture of the Pope. The 46-year-old singer's posting on her official website came in response to Miley's claims she based the video for ballad "Wrecking Ball" - in which she is seen licking a sledgehammer and writhing around naked - on her own 1990 stripped-back hit, "Nothing Compares 2 U." Sinead pleaded with Miley to stop sending a "dangerous" message to her female fans and insisted she doesn't need shocking theatrics to be successful because she has too much "talent."

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