LONDON — Irish chanteuse Sinead O'Connor has waded into the Miley Cyrus controversy, warning the young singer to avoid being sexually exploited by the music industry. O'Connor posted an open letter to Cyrus on Thursday after Cyrus told journalists she had modeled her “Wrecking Ball” video on O'Connor's famous “Nothing Compares 2 U.” She warns the former “Hannah Montana” star that it would be self-defeating to market her sexuality. The advice didn't go down well. Cyrus responded on Twitter by mentioning O'Connor's struggles with bipolar disorder. In a reference to troubled actress Amanda Bynes, who has been treated in a psychiatric hospital in California, Cyrus tweeted: “Before Amanda Bynes...There was...” and posted O'Connor's own tweets about seeking psychiatric help. — AP