The Cupcake Diaries: Mia's Baker's Dozen by Coco Simon
Mia is getting used to her new family now that her mum is remarried to Eddie and she's gained a new stepbrother, Dan. She's in the groove of going to her dad's house on the weekends, and everything is going pretty well at home and at school. Well, except for Spanish class. Mia's parents and stepfather speak it and she does too - but speaking it and writing it are two different things, and somehow Mia ends up in the hands of the merciless Mrs Alvarez and almost failing Spanish class. Still, things are so good at home that Mia doesn't want to worry anyone or rock the boat. But when her parents find out - all three of them - she realises that instead of having two parents, she's lucky enough to have three, and all three of them pitch in to help her. A baker's dozen is a bonus!