Her messages to others alleging promiscuity or sexual impropriety on your part sound defamatory. You should consider filing a criminal defamation complaint against her. It is a punishable offence.
While she may argue that they are true, she will have to prove that. Further, she will have to show that such statements are actually necessary for public good. Truth alone isn’t enough.
You can also file a civil suit against her to recover damages on account of her defamatory statements. The criminal complaint and civil suit can run in parallel.
First things first, send her a legal notice to immediately cease such defamatory messages.
Hope that answers your query. Follow-up questions welcome.