All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
We advise you to turn to Allaah seeking His help and supplicating Him to protect you and your husband from the evil of this woman. There is no specific Du'aa’ for this purpose. We have mentioned in Fataawa 83448 and 88814 the principles that should be observed in relations between a man and marriageable woman; as your relations with your brother in law and your husband’s relations with his sister in law.
Allaah Knows best.