She’s writing this stuff on her Facebook page or someone else’s? Who is reading the stuff she posts and what impact has it had on how others deal with you? What efforts, if any, have you made to talk to her about these statements and what was her response. Some additional details might help folks here offer some useful suggestions for you.
You have the option to sue her for defamation if she is making untrue statements of fact about you to other people and either seek monetary damages and/or an injunction to require her to take down the defamatory comments. But that can get expensive, particularly if she decides to put up a fight over it.

