Time to consult the professionals, Op. Speak to an attorney who specializes in family law. Find out what it takes to get a Cease/desist/Restraining order. You should ask if unauthorized posting of a minor child’s pics qualifies for action under any statutes that try to protect kids from internet crime.

Contact the website she’s posting the pics on and request they be taken down because parents did not give permission.

As the other commenter said, contact the school and inform them an estranged relative has threatened to show up at the school. Give them a picture. You can also contact the district safety office and ask about protection protocols to protect kids from estranged & dangerous relatives. The more info you know, the better able you are to protect your child and yourself.