"Any idea why the diagram shows a diagonal path from Kathy's home over to Joyner St? I'm wondering if there was a vacant lot that residents used to cut through from Lutie over to Nolensville? "
The short answer is, yes. I want to put up a more detailed post later with images and documentation when I am able, but for now to describe it:
Fire Station 21, at 320 Joyner Ave., was the shortcut. The building there today is just a few years old at most, but the original fire station from what I've found thus far seems to have been built in the early sixties. It had/has a back entrance driveway that goes north up to Lutie St. Before the station and driveway was built a house would likely have been there, at 315 Lutie Street. The driveway, then as now, is bordered by houses at 313 Lutie on the east and 317 Lutie on the west. It is between these two houses, going south down the driveway behind the fire station, that Kathy would have walked (according to the newspaper map).
She then would have turned slightly to the right, going from directly south to going southwest, along the western edge of the fire station, cutting diagonally across the parking lot at 2612 Nolensville Pike. That parking lot, and 2612 Nolensville, is there today, the northeast corner of Joyner and Nolensville. Today 2612 Nolensville is a Cash America Pawn, but it appears the building is a re-purposed grocery store. From what I have found, the building was built in 1950, so it would have been there at the time. A contemporary newspaper account says a witness saw her that night crossing a grocery store parking lot at the Joyner/Nolensville intersection.
This parking lot on the northern corner of Joyner, at Nolensville: From what I have read thus far, that was the last known sighting of her.
The parking lot fronts onto both Nolensville and Joyner. Joyner makes up the southern border of the parking lot, so she would have crossed the parking lot, going from the northeast towards the southwest, exiting the parking lot onto and across Joyner, and on to Nolensville.
So far I have not found any info on witnesses who saw anything after that.