How is the expiation for an oath (kaffarat al-yamin) to be given by a student living with his parents: Is it from the household food or from his personal allowance?

The questioner (sister) must pay the expiation for the oath from her own money. If she is unable, then she must fast for three days. If her father gives her permission to pay the expiation from his money, there is no harm, otherwise, it is not permissible, due to the saying of the Prophet, peace be upon him: "The wealth of a Muslim person is not lawful except with his good will."