Is a wife sinful if she refrains from visiting her husband's sisters after being psychologically harmed by them, even though they continue to visit her, and this is due to her inability to forgive?

The wife is not obligated to maintain ties with or visit her husband's family if there is no kinship between them. However, one should be keen to observe the general rights of brotherhood. These rights are affirmed by the marital relationship (in-laws). Muslim narrated from Abu Dharr that the Prophet (peace be upon him) said: "Indeed, you will conquer Egypt, a land where the qirat is mentioned. When you conquer it, treat its people well, for they have a covenant and kinship." Al-Nawawi said: "The 'covenant' (dhimmah) refers to sanctity and right... and the 'kinship' (rahim) is because Hagar, the mother of Ishmael, was from them... and the 'in-law relationship' (sihr) is because Maria, the mother of Ibrahim, was from them."

The frequent disagreements between the wife and her husband's family should not escalate to harming either party, as harming a Muslim is forbidden. Al-Tirmidhi narrated from Ibn Umar that the Prophet (peace be upon him) said: "O community of those who have submitted with their tongues but in whose hearts faith has not entered, do not harm Muslims, nor shame them, nor seek out their faults."

It is better to strive for reconciliation, forgiveness, and accepting excuses, for there is great virtue in that. The mother should help the children maintain ties of kinship, because severing them is a great sin, and maintaining them is obligatory.