Answer: The White Queen lied about eating some tarts, causing her sister to be blamed.
Mirana and Iracebeth were princesses who grew up to be the White Queen and the Red Queen respectively. Mirana stole a jam tart from her mother's kitchen, but denied any wrongdoing when questioned by her mother, the Queen. Iracebeth got the blame and ran out of the room in tears. Iracebeth ran out of the castle, into a town square, and banged her head. From that moment, her head became larger than normal and her personality took a turn for the worse.