Is boycotting my neighbor, who was my friend, a sin, and merely greeting her sufficient, considering she was a bad companion who negatively affected my faith, and her attachment to me reached the point of admiration, which compelled me to reduce contact with her after failed attempts to clarify the situation, and then she joined the Qur'an memorization center I attend and turned away from me, not greeting me?

The Shari'ah commands good treatment of neighbors and forbids estrangement and abandonment. However, if associating with a neighbor harms a person's religion or worldly life, then there is no sin in abandoning them. Ibn Abd al-Barr said: "The scholars unanimously agree that it is not permissible for a Muslim to abandon his brother for more than three days, unless he fears that speaking to him or connecting with him would corrupt his religion, or lead to harm to himself in his religion or worldly life. If that is the case, then he is permitted to avoid him and keep his distance. And sometimes, a beautiful cutting off is better than a harmful association."