Does a divorce take place if the wife's sister does not apologize to the mother, and is a visit without uttering an apology considered an apology that annuls the oath?

Conditional divorce, according to the majority of scholars, takes effect if the condition is met. The intention of the husband is to be considered. If you intended that your wife's sister's apology for her verbal utterance (to your wife) was the condition, and she did not utter it to your mother, then her visit to your wife or your wife's visit to her would trigger the divorce. However, if you intended the apology to include everything that falls under its customary meaning, and your wife's sister's visit to your mother is customarily considered an apology, then the condition for divorce is nullified. And if by "preventing the visit" you merely meant her coming, then the divorce occurs upon her coming. But if you intended to prevent her entry into the house, and she did not enter, then the divorce does not occur. It is advised not to use divorce pronouncements for threats or oaths.