Does the third divorce occur if she enters the house of my sister's husband to visit her, after she swore: "My wife will be divorced if I or my wife enter his house for the rest of my life, or if he enters my house"?

The jurists have divided divorce into immediate and effective, and conditional upon a time, characteristic, or condition. The majority of jurists hold that conditional divorce takes effect when the condition is met, whether the intention was to bring about the divorce or if it was for an oath. Ibn Hazm, however, believes it does not take effect. As for Ibn Taymiyyah, he elaborates: if the conditional divorce has the meaning of an oath, it does not take effect, and an expiation for an oath becomes due when the condition is met. If it was not intended as an oath, then it takes effect when the condition is met. Therefore, the divorce you made conditional takes effect according to the majority when the condition you made it contingent upon is met. The problem of lack of communication can be resolved by meeting at the home of a relative or neighbor, especially since you have divorced her twice before.