Does the incident of sexual harassment and potential rape of the wife's daughter by the husband automatically nullify their marriage, and if not, how can the mother nullify this marriage?

If a man commits adultery with his wife's sister, mother, or daughter, his wife does not become unlawful to him according to the majority of scholars. This is based on the understanding that nikah (marriage) refers to the contract, not the act of intercourse, and adultery does not entail the rulings of nikah, such as sadaq (dowry), iddah (waiting period), or inheritance. Therefore, if it is proven that the husband assaulted his wife's daughter, this unlawful act does not make his wife unlawful to him. The wife, however, is permitted to seek annulment of the marriage from the judge due to the husband's transgression and immorality, or due to his absence from the home. This is called "divorce for harm" (talaq lil-darar), which encompasses anything that causes physical, psychological, or moral harm to the wife.