After sitting and thinking about this case for hours, I have decided that I completely agree with Emeralgem and snowbunny, there very well may have been foul play involved. Gail has been gone a long time, and I think had she needed a break she would have surely felt like coming home by now.
However, I am inclined to believe that AD or the siblings are the ones that are hiding something.
AD is constanty talking, constantly bashing and accusing Matt. I think she may be trying to divert attention from herself. First we have the run Gail made to Birmingham around Easter. Of course the police report hasn't been released to the public, but we know that Gail ran away from the lake where AD was and to the other people in Birmingham. It also seems so odd that on the 30th, Gail called Diane in NY multiple times, she talked with LE on signal Mtn. She even, according to some people, called Matt, but she CHOSE NOT TO CALL her self proclaimed best friend AD? (who btw she had plans with that day and who lived close to where she was?). Makes no sense. Either Gail had to have some mental issues going on which really affected her judgement, or maybe she was trying to sneak away from AD. If AD's statements are true, then she was very involved in Gails life. She also was pushing Gail to do things, i.e. get a PI, put a tracer on Matts car (which I think is illegal), file for divorce. Maybe Gail got tired of being pushed. AD has stated that Gail was afraid of Matt. If she were that afraid of Matt, there's no way she would run away from her best friend (without telling her) and back to SM and Matt (calling him to let him know she was coming) and then leave the kids there with him. Absolutely no way on this earth a mother would do that if she were afraid of the father/husband. So again, that doesn't make sense.