Invitation to the Dance a budding ballerina does a turn as a playmate The Roman orator, Cicero, once declared that nobody in his senses would think twice of dancing, and his fellow Roman, Terence, said dancers "seem to have more brains in their feet than in their heads." As a result of this lumpy logic, look what happened to Rome. We thumb our unRoman nose at those two and side with Havelock Ellis. Quoth he: "Dancing is the loftiest, the most moving, the most beautiful of the arts . . . it is life itself." And we think Sandra Edwards, our Miss March, would go along with that, too. Though a scant 18 years of age, she has studied art and modern dancing and is currently a soaring ballet pupil. Sandra dotes on non-fiction and has a deep-down, locked-in appreciation for just about all sorts of music. Sandra's ambition is to be tapped for membership in -- and eventually to become prima ballerina of -- a crack ballet group like Sadler's Wells. Margot Fonteyn is her model and her idol. A well-rounded miss, say we with absolutely no double meaning in our mind; a young lady who, disproving testy old Terence and sour old Cicero, is indeed in her senses and eminently endowed at both ends of her charming anatomy.