The Princess Diaries By Meg Cabot

Mia Thermopolis is pretty sure there's nothing worse than being a five-foot-nine, flat-chested freshman, who also happens to be flunking Algebra.
Is she ever in for a surprise.
First mom announces that she's dating Mia's Algebra teacher. Then Dad has to go and reveal that he is the crown prince of Genovia. And guess who still doesn't have a date for the Cultural Diversity Dance?