This lady sounds to me like she needs true taste of her own medicine. Are you absolutely sure she is the is the one doing it?

I would contact a lawyer and get things in motion to sue her for slander.

Get all the free legal advice you can and see if you can get a cease a desist order in effect that way if she doesn't stop you can sue her. She should also have to form a formal apology on your Site.

Fight back smart.