Unfortunately this is a difficult situation which is all too common. Your first option would be to get a PPO against the mother. PPO's can be used for many things, one of which is to stop harassment of the kind that you are reporting. Another option would be to file a motion for contempt of the parenting Order. Look closely at the Order, and if you can find specific language which she is violating, you are free to bring such a motion to get her to stop, or she risks fines or imprisonment.
Answered on Jan 12th, 2015 at 8:27 AM