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 ask Allaah to exalt his mention as well as that of his family and all his companions.
Fulfilling one's promise is among the noble characteristics which are encouraged by Islam. Allaah eulogizes those who have this quality, He Says (which means): {And mention in the Book, Ishmael. Indeed, he was true to his promise, and he was a messenger and a Prophet.}[Quran 19:54]. Islam dispraises breaking a promise without any religious reason and considers it among the characteristics of hypocrites. Prophet said: "The signs of a hypocrite are three: Whenever he speaks, he lies. Whenever he promises, he always breaks his promise. If he is entrusted, he deceives." [Al-Bukhari and Muslim]
Fulfilling a promise is desirable not an obligation according to many scholars. If the husband has promised his wife that he will allow her to go to visit her family then it is desirable for him to honor his words provided she is traveling with one of her Mahram (unmarriageable relatives). If she is traveling alone then he should not fulfill his promise since the traveling of a woman alone without being accompanied by an unmarriageable man is not allowed. The Prophet said: "No woman should travel except in the company of an unmarriageable man." [Al-Bukhari and Muslim]
We advise this woman to settle the matter wisely and perceptively. The husband should help his wife maintain good ties with kinfolks; it induces love, affection and brings happiness in marital life.
Finally, we draw attention to two matters:
First, a husband is not obliged to bear the travel expenses of his wife but it is among the noble qualities of a husband to bear those expenses.
Second, it is not compulsory for a husband to inform his wife why he has changed his mind. However, it is better to inform her about his decision if there is no considerable benefit in hiding it. On the other side, the wife must give her husband the benefit of the doubt as for why he is not informing her.
Allaah Knows best.