Esme Pepper by Jacqueline Wilson

Esme's mum would do anything for her, including trying to steal the expensive dolls house that Esme desperately wants. When Mum gets caught, Esme finds out that life in foster care can be challenging - especially when you're known as a bit of a troublemaker. When a placement proves hard to find, Esme has to stay with an elderly couple who have retired from fostering. She knows she only has to stay until Mum gets back, but she still has to deal with a new school, and a real idiot of a class bully. Esme might like to cause trouble, but this time she is going to have to find a way to get along.