When she stepped out on Saturday night, Miley Cyrus dazzled in a coral silk chiffon Jenny Packham gown and what looked like a very special accessory - the diamond sparkler she had already revealed on Twitter. "I am sooo obsessed with @jennahipp nail foundations!" Cyrus, 19, wrote Thursday in a posting meant to show off her manicure but sure couldn't disguise that ring on her left hand. The sizable rock has generated talk that she and Liam Hemsworth are taking their relationship to the next level and getting engaged. But, are they? While reps did not return requests for comment, a source close to the couple says they are not engaged.