How do I handle my awful neighbor?

No condo ociation but is there a property manager on site? Who handles these "common areas" that she's babbling about- someone must since they can't maintain themselves. Find out who these people are and go to their offices with your land survey and explain the situation to them. Perhaps they'd be willing to send her a registered letter doenting that this is in fact your space. But reading about her "elder" comment, she sounds like a looney toon who won't listen to reason anyway, but it's worth a shot.