As a brother, am I obligated to give my sister 12,0 pounds for her wedding preparations, which she claims my father promised her then denied, especially since she refused to take 5,0 pounds that my father gave her, saying, "This is your right and you have nothing else," knowing that her share of the inheritance is 70,0 pounds?

The sister's claim regarding the father's promise or the money paid to her and her returning it to him holds no weight. All that the father left behind is an inheritance to be divided among his heirs according to Islamic law. Issues of dispute are to be referred to the Sharia court or to the people of knowledge (scholars) in the country.