Cell towers: Someone posted about the lack of towers on the island. This is irrelevant. Doesn't matter that there's a close tower, location is determined by triangulation of available towers. If you can get a signal, you can be found.
Polygraph: Someone posted that a reliable source stated that the polygraph(s) indicated deception. We all know this is inadmissible in court, HOWEVER it's a good sign -- if she failed her polygraph(s), she's not as good a liar as she thinks she is, and this will factor into her confidence level. A polygraph alone doesn't detect deception. A skilled polygraph examiner can use it to put the screws to her and make an educated assessment of deception. Failed polygraphs may also indicate that she's not quite as much of a sociopath as a lot of us might feel. A true sociopath would probably pass the test.
Facebook: The "Facebook Mobile" is not a reliable indicator for mobile posting. While my phone can post via Facebook Mobile, my phone also has a browser which would show on Facebook as a regular internet browser. TH is tech-savvy, that's my assumption, this is feasible. And yes, LE can definitely subpoena all logs from TH's FB account, which would indicate proof positive where the posting came from (the IP address of the source would indicate home broadband, phone broadband, some random unsecured wifi, etc.) -- combined with triangulation, they could even tell where she was when she posted it.
Arrest: When they have enough evidence, physical or circumstantial, to charge her with a crime. Sounds like soon to me.
Tech-savvy: Keep in mind that she and the family are not only tech-savvy, but interested in crime drama. There's a good chance she's following the threads here as well.
