LONDON (Reuters) - American pop star Miley Cyrus has snubbed some prim motherly advice about her new bad girl image from Irish singer and sometime rebel Sinead O'Connor. The "We Can't Stop" singer - who has ditched her squeaky clean Hannah Montana Disney image for a solo singing career as a tattooed sex siren - rebuffed an open letter from O'Connor calling on Cyrus to tone down her sexualized persona. "Sinead. I don't have time to write you an open letter cause I'm hosting & performing on SNL (U.S. comedy show Saturday Night Live) this week," Cyrus tweeted. ...