Is the eldest working daughter obligated to allocate a portion of her savings to pay off her deceased father's debt, or is she not bound by that and may she save money for her personal use, such as marriage, buying a car, or performing 'Umrah, especially since there is income from a building, a portion of which is allocated to pay off the debt?

Paying the debt of the deceased is obligatory upon their heirs if the deceased had wealth, based on the Almighty's saying: (after any bequest has been fulfilled or debt paid). Thus, they do not inherit anything until after the debt and bequest have been settled. However, if the deceased had no wealth, it is recommended for their relatives—especially their sons and daughters—to pay off their debt. This is an act of righteousness and kindness towards them, but it is not obligatory upon them. Therefore, your payment of your father's debt is an act of righteousness towards him after his death, and you will be rewarded for it.