Jennifer's body was located in the Pharsalia Woods (the woodlands that encompass New Michigan, Pitcher Springs, Perkins Pond, and Pigeon Hill State Forests). In particular the New Michigan State Forest area.
http://www.cnyhiking.com/FLT-NewMichiganStateForest.htm
On the map on that website, the Plymouth Loop section of the Finger Lakes Trail crosses just south of the area where Jennifer's body was discovered (just East of Coy Street, along Center Road).
Here's a link for the Plymouth Loop itself:
http://www.cnyhiking.com/PlymouthLoop.htm
On that map if you were to go from Plymouth Lean-to and head on a bearing due north, heading towards Center Road, you'll pass over, or very near the spot where Jennifer's body was located.
Another thing to point out is at that lower part of that page, it calculates the distances between each of the points along the Plymouth Loop as being 6.8 miles.
6.8 miles isn't exactly, but is fairly close to being a quarter of a marathon distance which is approximately 6.6 miles. It'd be a good place to run if training for a cross-country marathon run, or a run in which there will be varying terrain and moving up and down heights.