The Witch Stories by Erica Morrison

Esmeralda is a shy witch who longs to be noticed. This year she and her cat Pickitywick are attending The North American Spell In, a large witchís convention and she has a plan to get the attention she deserves. In an old spell book she finds a mysterious recipe for Changing Tea and brews up the potion. The spell is supposed to turn you into the person you have always wanted to be, and seems to be working very well until events happen that make Esmeralda question if the magic is from a spell or located deep inside herself.