Does the oath of the deceased father become null and void if he swore his daughter would not work unless she married a certain man, then he died and she did not marry that man? And is it permissible for someone to make expiation for the oath on behalf of her deceased father?

A father does not have the right to force his daughter to marry someone she does not desire, and her refusal to do so is not considered disobedience (ʿuqūq). If the father swore an oath to his daughter that she would not work unless she married a specific person, and then the father died: if the daughter had worked during the father's lifetime, the expiation (kaffāra) would be incumbent upon the father and paid from his estate. However, if the daughter did not work during the father's lifetime but worked after his death, no expiation is incumbent upon the father because the oath expired with his death, and neither marriage nor expiation is incumbent upon the daughter.