Is my wife entitled to claim anything from her deceased father's inheritance, given that her mother has executed a contract, signed by everyone, including my wife, authorizing the mother to dispose of the inheritance, and my wife's brothers are utilizing the father's residence?

The daughter has a right to her father's inheritance unless there is an impediment to inheritance (slavery, murder, difference in religion). If the wife appointed her mother as an agent to manage her share of the inheritance and believes she overstepped, she has the right to dismiss her and revoke the agency, because agency is a permissible contract. The inherited dwelling is a right for all heirs according to their legal share, and the children are not entitled to monopolize it without the rest of the heirs. The wronged party may refer the matter to the Sharia (definition) court.