Cassidy was born in
Coventry,
Warwickshire. She was a student at Liverpool Polytechnic (now
Liverpool John Moores University), where she studied illustration. She has written over 30 novels as well as novellas, e-books and non-fiction. As is common in young people's literature, many of her novels are written as series, such as the
Daizy Star books for younger readers, and the
Chocolate Box Girls for a relatively older audience. Cassidy made all the illustrations for the
Daizy Star series herself, including the front covers. She also spent 12 years as the
agony aunt for
Shout, a magazine for teenage girls, and has taught art at local primary schools. == Personal life ==