You already know Siobhan because you’ve heard every story about how she danced on the bar at Chateau Marmont and stole a rock star’s heart. You’re never quite sure where she’ll turn up next, but you’ll know when she arrives. Siobhan is a force of gravity in Studio 54 sequins and a leather jacket, blowing you a kiss as she runs out the door. Someone says she was last seen driving off to Vegas in a convertible. Another says she was spotted swimming in the moonlight in Monaco.