A defamation lawsuit is a long and expensive process with a highly uncertain outcome. Try first for a civil restraining order. That may solve your problem, and it will create an official record that you dispute her statements. It is cheap and fast, relatively speaking.
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I generally agree with Ms. McCall, especially respecting the idea of a defamation case. However, I suggest that you at least see an attorney with any of the actual statements this person has made to help you evaluate the potentil success of a restraiing order as restraining speech is very difficult.
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