It was the first chapter book I remember reading, my teacher suggested it (ie I read it at school so parents can't help here). I think the cover was white, and I have a feeling the girl (main character) had red curly hair but I may be imagining that.
She kept saying things like jumping Jellybeans etc as a way of showing surprise. And I have a vague recollection there was something about buying new shoes too.
Anyone?!