What should the questioner do, as she has hurt her friend with words and apologized to her many times, but her friend has not forgiven her?

A Muslim should not refuse to accept his brother's apology if he has wronged him and apologized, for accepting the apology of the apologizer is a sign of good manners and the characteristics of noble people. If the offense was in words as a response to a previous offense from her and without exceeding the bounds of retribution, then there is nothing against you. However, if you were the one who initiated the offense, then you are the oppressor, and you must continue to try to seek her forgiveness and seek Allah's help. If she forgives, then that is good. If she refuses, then make many supplications for her well-being.