Nothing specific, unfortunately.

I'm not local and have zero inside info, but I have an active imagination and sometimes, intuition. Having read about the mountainous roads in TN and the possibility that she was heading to AL or even NY (long drives) or wherever, it just seems too possible that she could have been followed/intercepted and run off the road. Her red Jeep should be very visible but as many have posted, the summer foilage may conceal it or it may be underwater. Or it may be otherwise hidden (nefariously...stowed somewhere, burned, chopped, etc.).
I'm still wondering about SB's sighting of Gail (who didn't acknowledge SB), and the sighting by CC (including Gail meeting with someone in a pickup truck). Gail may have been kidnapped or Jeep-jacked.
I don't think that Gail intended to disappear, either alive or by suicide. I think it was foul play or extremely unlucky accident (Jeep hard to find). JMHO...MOO!!!