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You would first need to sue her. Facebook is a public forum and so they generally are permitted to allow people to post things unless they KNOW them to be untrue. Just your telling FB that the information is untrue is not enough, because she can just say "yes it is" and then FB is stuck in the middle, without any real ability or obligation to reach the truth. They aren't a court.
So, you should sue this individual in small claims court so that it is not expensive and it can be fast. You can do this yourself just by contacting the county court where this person lives. Once you take that person to small claims court, you can have an injunction issued against further harassment and you can use that adjudication to send notice to FB. Then FB will have notice of a determination that the statements are slanderous and if they STILL allow them, you can sue FB.