IMO, the more you interact with her in ANY way, the higher the chances are for her getting into your head. And the longer this goes on, then, like the above story, you might be more likely to end up with a psycho and get a brick through your window.
With old bitches, I always spoke my mind with a degree of class, like Junkyarddogg suggested, and I leave ZERO room for ANYTHING. They know NEVER to come even talking to me ever again because I am in control of the situation by putting them in their place and I am the superior person.