Is it permissible to disobey a father who insists that his daughter study Islamic Law, when she wishes to pursue another field of study without his knowledge?

A father does not have the right to compel his child to study a major they do not desire. Therefore, you are not obligated to obey your father in this matter. However, your father is not required to financially support your university studies, and if he does, it is a donation. It is not permissible to use donated money designated for a specific purpose for another purpose. It is important to emphasize the great right of a father and the necessity of honoring him.