Did Allah send this woman to expose the questioner, and will Allah take revenge on her behalf against those who harmed her and her family and defamed them?

If the woman is falsely accusing you of a secret marriage, then she is unjust and must repent. Her statement, "If I were innocent, Allah would have stopped me from accusing you," is false, for Aisha - may Allah be pleased with her - was accused while she was innocent. If you fear Allah and rely upon Him, Allah will suffice you and repel the stratagems of plotters from you; Allah Almighty says: "Indeed, Allah defends those who have believed." Allah Almighty informs that He defends His servants who rely upon Him from the evil of the wicked and the stratagems of the immoral, and He protects and grants them victory.