Disruptive family members can cause havoc, especially at Christmas, which you must be all dreading if you and your husband are the only family members she now has any contact with.
I don't know how close she lives to you and whether you can get her involved in some local social activities which might help her diflect her time and energy more usefully elsewhere. Perhaps her local GP and community health team might have some ideas.
It might help if you maintained some very limited contact with her, but always at HER house, so that you can be in the driving seat and decide when to leave if things get difficult, rather than having her at your home, where you are trapped if she won't leave. Short of having an ex-director phone number I don't know what else you can do, except close the curtains and pretend not to be at home if she calls.