Would the female heir be sinful if she left her share of the inheritance to her brother so that he could restore the rights of their paternal aunts, knowing that there is a dispute over the amount the grandfather possessed, and that the aunts had previously refused to take the money?

If the properties are registered in your father's name, the default is that they belong to him. Whoever claims they belong to your grandfather must provide legal evidence. If they fail to do so, then the properties are yours. If the court ruled in your father's favor, the ruling stands, unless you are absolutely certain that they belong to your grandfather. This is because a judge's ruling does not change reality if it contradicts it, as confirmed by the Prophet, peace and blessings be upon him: "If I rule for someone concerning the right of a Muslim, then it is but a piece of fire, so let him take it or leave it." You must compel your brother to return the right to its rightful owners. Such matters require being brought before a Sharia court or consulting scholars and listening to all parties, as the Prophet, peace and blessings be upon him, said to Ali: "Do not judge between them until you hear from the other party just as you heard from the first."