Is boycotting considered a sin if it is impossible to forget the offense from the other party, especially since she is unable to initiate conversation with her?

First and foremost, repentance to Allah is obligatory, as mixing (of sexes) and disobeying Allah are among the greatest sins. A Muslim woman should not disrupt her friend's marital life by revealing her husband's sin, for Allah's right takes precedence over the wife's right. It is forbidden for a man to have sexual relations with any woman who is not his wife, and this is considered an aggression, especially if she is his neighbor's wife. Furthermore, a man's betrayal of his wife by committing unlawful acts can lead to health, psychological, and familial harm, which affirms the wife's right to seek divorce due to harm. The woman mentioned must boycott the immoral man, hasten to repent, distance herself from forbidden mixing, and adhere to the hijab. If she cannot preserve her religion in her current job, she must seek another job where she can preserve her religion and honor.