Is it permissible to abandon a friend who insults and hurts, and who caused a rift between the questioner and her friends, given the questioner's resentment toward her friends who believed that friend, and is it permissible to supplicate against her?

It is not permissible for a Muslim to abandon his brother for more than three (days), and anything beyond that is a great sin and a reason for its perpetrator to be deprived of the forgiveness of his sins. The corruption of mutual relations is among the destructive things that shave away religion. Therefore, one must be keen on reconciliation, initiating greetings of peace, and showing forgiveness and tolerance. If attempts at reconciliation are not fruitful, then a graceful abandonment is permissible for one whose companionship is harmful, while fulfilling the obligatory rights. As for supplicating against the oppressor, it is permissible, but forgiveness and pardoning are better.