I am glad I searched for this. There was more info than I recalled.
A worker at the mountainside market deli said police came there at 7:15 PM (Before she was found). The police said they believed that Vanessa had been to the market around noon for a drink.
http://www.telegram.com/news/20160808/unimaginable-act-sets-princeton-on-edge
This fits precisely with my supposition that she was hydrating for her run and that someone could have seen her at this point which was not long at all before she set out.
Thank you for the information on that. It just doesn't show me that she was talking about running and this person followed her home and waited for her to leave, picked a location to attack her so close to home and had the means in his vehicle to do what he did, etc.