Will God take revenge on the friend who wronged the questioner and tarnished her reputation, given the questioner's desire for revenge?

What your friend did is a great injustice. Likewise, the friend who helped her is a partner in sin. Allah will take retribution from the oppressor unless the oppressed forgives him. Do not seek revenge yourself, so that you do not fall into injustice. Rather, entrust your affair to Allah, for He will take care of it. Know that adversaries will gather before Allah on the Day of Resurrection, so that justice may be exacted for the oppressed from the oppressor. You may also refer her case to the court to have the Hadd punishment for slander applied to her.