What is the ruling of Islamic law regarding a wife staying with her husband in his family's home, given that she is subjected to theft by his sister, and her husband does not intervene for fear of his mother's anger?

It is your right upon your husband that he provide you with a private dwelling separate from his family, and you have the right to demand this. You must think well of your husband's sister and not accuse her without evidence, and safeguard your money. We advise you to be an aid to your husband in obeying his mother and showing her kindness, and to endure her anger to preserve your home and marital happiness, because the outcome of patience is good. Allah Almighty says: "Indeed, the patient will be given their reward without account."