From the beginning, one thing that remained constant in my thoughts is that Greg made contact with her that monday. He said he didn't and sounds convincing but remember he is an addict and addicts lie.
If it was just a fling, he would not have made contact with misty and called her monday, the 9th. He was either smitten or there was a drug setup for that day. At some point, I believe they hooked up.
Wasn't Lisa asking misty when she was going to see her Dad who was air-flighted to Gainsville and in the hospital having surgery? Did misty ever make it there? Chelsea managed to get there but we never heard anything about misty being there. I doubt she ever went. She called there @ 2:00am (do we have exact time?) to talk to her mom about Haleigh though.
The first time I noticed how slick misty was was when she was interviewed by AH. She would slip and very quickly cover up her blip...before most would notice. This told me she was pretty good at fooling people...and her mind was in full function mode...at least as far as protecting herself.