First of all, there is evidence that Westerfield was watching her. Apparently one of his upstairs windows faces her bedroom (the houses are on hill, with Westerfield's UP the hill from the Van Dam's), and they found binoculars by the window, pornagraphic materials, and evidence that the blinds on that window had been repetitively pulled down in the middle as if to peek out (and there were slightly dirty areas around the pulled down in that section). Only Westerfield's finger prints are on it.
We've seen the photos of the neighborhood...that sounds like bs to me