My fiance's ex wife is a nut. They have two kids together, which he has placement of and 75% custody of. She constantly bad mouths both him and I. Tells people he does drugs and that I do drugs, that we don't care for the kids, that we spend our money on drinking and partying. That I don't pay for anything (although I do pay for the kids clothes, his clothes, and my own clothes, and vet visits for the animals), she calls me a bimbo and stupid and posts these things on Facebook, she is ONLY supposed to call him Monday's at 9 am but that harldy happens and she calls further during the week just to ***** about whatever. Is there a case there? Is there ANYTHING I can do about it.

You can have an attorney enter a petition for an injunction to stop these behaviors and if she continues, she can be held in contempt and put in jail. That it's on Facebook is helpful as you can obtain proof of the behaviors.

Libel laws could also apply but I'd probably manage it through the family court personally.

I'm not an attorney - work for one as a paralegal in family law - but call a family law attorney and ask in your jurisdiction.