Is the questioner considered sinful for not reconciling with her brother's wife, especially since she intentionally ignored her, and her family refuses reconciliation to preserve their dignity?

Satan seeks to create enmity and hatred among Muslims. Therefore, the Quran commanded good speech to thwart him, and the Prophet forbade turning away from one another, hating one another, and a Muslim forsaking his brother for more than three days.

So, if the boycott of the brother's wife is for no legitimate Shar'i reason, it is not permissible for more than three days, and the estrangement ceases simply by extending greetings.

However, if the boycott is due to her sins, it is legitimate, with the obligation to advise her and explain the reason for the abandonment. It might even be better to cease the boycott if that is more beneficial for her to accept advice.

Being courteous to others, even if with some effort, breaks enmity, and responding to ill-treatment with kindness creates affection. Forgiveness increases honor and brings Allah's forgiveness.

Giving up covetousness for what others possess and striving for Allah's pleasure earns people's respect. The hadith "The believer is sagacious and shrewd" is weak.