Philippa Fisher's Fairy Godsister

Description for PHILIPPA FISHER'S FAIRY GODSISTER by Liz Kessler:

Average eleven-and-a-half-year-old Philippa Fisher would like nothing more than a fairy godmother. Instead, she gets Daisy, her same-age fairy godsister. Philippa is thrilled. Now she can wish away her shyness and win over her classmates. She can even make her free-spirited parents just a bit more normal. Daisy, who's not too fond of humans, only wants to grant the wishes as quickly as possible. But things are never that simple. The pair just can't seem to get along, and Philippa's wishes keep making her life worse. Will Philippa and Daisy come together to solve the mess they've created before it's too late?

This is #1 in Philippa Fisher Series.