She either had a car parked nearby that she knew would identify her or she actually lives nearby. Based on how she's dressed I'm going to say that she lives nearby. She lives within whatever radius is a comfortable walk for a person of her physical condition. If she has the temerity to tear down a political sign on private property in daylight she also wouldn't be likely to give a hoot if she were seen driving away.

$500 is enough money for someone to start posting signs with her picture throughout that neighborhood. This won't take long.