She has a comic way of moving, as if to a tune in her head that no one else can hear. Hers is a fine comedy performance. A comedy with fine possibilities has been left all alone on the Dorset stage without a rope to hold on to. “Advice” plays at the Dorset Theatre Festival in Dorset, Vt, through August 15. For information and tickets, visit Dorset Theatre Festival’s website or call (802) 867-2223.