Does one sin if they supplicate against a person from whom they have suffered harm, and then, upon learning that something bad has befallen that person, say, "I supplicated against her"? And is their sorrow over what befell the one who harmed them considered forgiveness for that person, despite the continued harm from them?

The first is to forgive those who have wronged you, seeking Allah's reward. If you supplicate against her in proportion to the injustice she inflicted upon you, there is no sin upon you. There is also no sin in informing her of your supplication against her; that would be a form of self-vindication. If you miss the virtue of forgiveness, then strive to supplicate for her healing and guidance. If she repeats the injustice, respond with forgiveness, and strive to involve people of goodness to resolve the issues. If you have a right, then involve someone who can remind them of Allah and instill in them fear of His punishment.