It's been my opinion all along that KC may have turned her phone off or left it somewhere when she went to dump the body.
Remember she isn't the brightest little bulb on the tree, but she is very conniving, that's a given !! She was a real CSI buff and knew they could follow the phone trail, so someone alittle smarter than her needs to figure out where she could have put her. Also there are the 3 dead areas. I think it might take some time, but a good sleuth in here can possibly back track her movements.

For example, she may have turned it off and then turned it back on before heading to wherever she was going. She probably did this after she traveled a couple of miles from the site. If someone can find a pattern for those dead zones that matches at least two out of the three, that may be the missing link here.
I know I'm sounding confusing, but see where she traveled when the phone pinged a tower afterwards, like was it SW or NE etc etc.
Also take into consideration that she knows she was spotted maybe and moved the body. I said earlier that the guy who saw her by the tracks, Kovach and his friend. I think she decided not to leave her there as he said she struggled with a bag and bumped her head on the car trunk. Sounds to me that it was heavy otherwise she could have easily slung it into trunk.
That is a very telling clue, and again the perp always goes back to the scene at least more than once.
I would study the pings and maps, but they are so confusing to me, I'd be of little help.
So where did she go after that?? Also the other woman who spotted her, did she spot the woman??