Is it permissible for a female employee to take a 3-day leave after postponing a work assignment she received with the approval of her employer?

An employee is not permitted to exploit leave days without referring back to the employer. The default is for her to return to her work, unless the authorized official grants her permission. These matters are subject to the applicable regulations and laws, and the conditions agreed upon at the time of the contract. The employee is obligated to adhere to these regulations, based on the words of Allah the Almighty: "O you who have believed, fulfill [all] contracts," and the words of the Prophet, peace and blessings be upon him: "Muslims are bound by their conditions."