``Bothered'' is just the right word to sum up the flavor of this refreshingly mild case of sibling distress. What bothers Kate is little sister Tory, look-alike and copycat—that is, until Tory gets big enough to have friends of her own. Then Kate finds she misses the adulation, and even the company. Noll rounds out her cast with a wise, sympathetic mother and provides boldly designed illustrations that make striking graphic use of the girls' similarities and reveal Kate's affection for her sister long before Kate herself is aware of it. An appealing story with unusually attractive illustrations. (Picture book. 4-8)