The easiest way to catch her on video.
http://www.cabelas.com/cabelas/en/templates/index/index-display.jsp;jsessionid=03BLWZZ3WIVJWCWQNWRCCOQK0BW 0GIWE?id=cat20098&rid=0180101070502&cmCat=perf&cm_ ven=performics&cm_cat=Google&cm_pla=optics_camera& cm_ite=hunting%20camera&_requestid=23919
Do everything legal. Don't let anything backfire on you. Then take her to court for car washes, buffing out scratches, etc. Maybe contact local paper for a story based on malicious mischief and endangering the welfare of a child. Especially if you have filmed evidence of her doing in front of her kids. Contact child welfare agency. You can make her life a hell by doing everything legal.
Hate those people who think their opinion is more important then yours.
Don't get mad, get even.