Legal Question in Criminal Law in California

Insults to be defamation must be untrue statements. An insult by itself may not be defaming... There may be a couple of invasion of privacy torts that you could use... A cease and desist letter may be a good start

Mr. Green is right. But there's more to defamation than falsity. The statement must also be made where others can see or hear it, and it must harm your reputation with those who learn of it.

Note that you posted your question under criminal law, but defamation is not a crime. It's a civil wrong, which you can address via a civil lawsuit.

If there is a family law matter pending you bring the issue before the family law judge, particularly if there is any way that the insults can get back to your daughter.

You may have something that is actionable on a few levels. feel free to call my office 818 345-0123