What is the Sharia ruling on the the opinion of the eldest sister, and is a rightful heir allowed to impede the division of an inheritance, even if such a delay causes harm to everyone?

None of the heirs has the right to impede the division of the inheritance or to harm others. If the property cannot be divided in a lawful manner that allows each heir to dispose of their share without harm, then any heir has the right to request the sale of the property and the division of its price. If one of the heirs refuses, the judge shall compel them to do so. If resorting to the court will lead to the sale of the house at a low price, the questioner should try to agree with the heirs on a method for division or sale of the house, or resort to an arbiter whose judgment they accept.