Keep in mind that the AA is to show probable cause for an arrest. It contains the info needed to get her arrested. Meaning it doesn’t need to show/tell when they started looking into her or why.
We could find more about that out at her 2/3 hearing but I think they were on to her way before 12/18. Like as in as soon as they ruled out SC.
As much info that was released there is still way more that wasn’t. IMO
That's true and you may be right that LE was onto MF way before 12/18.
Just based on what we know now though, I don't get the sense that MF was at the top of LE's radar prior to the eyewitness coming forward, for several reasons.
--No one in Heidi's world reports to have suspected MF of faking her pregnancy or being involved in the disappearances (instead they shared information with MF, said that she seemed very concerned, and expressed shock when LE honed in on MF); per Heidi's friends' interviews.
--It wouldn't have been suspicious at all that Heidi's last phone or text conversation had been with her very good (supposed) friend MF, especially since MF reportedly volunteered the date/time/supposed content of that communication freely; per Tim Miller's interview.
--LE did not request or make an in-person visit to MF to interview her (and get a feel for her reaction) regarding her good friend's disappearance; per Tim Miller's interview.
-- In Shane's friend's interview after MF was arrested, he said that Shane had told him he'd been grilled by LE about MF. Even so, it doesn't seem odd, to me, if LE was grilling Shane about himself, MF, and likely many other people close to Heidi (especially since, per Tim Miller, MF had pointed the finger directly at Shane).
--I haven't seen anything to indicate that Shane had been ruled out of any involvement prior to MF's arrest. I tend to believe that LE was working parallel angles before they had evidence that Heidi had left the apartment of her own accord after getting home from the school book fair and before being reported missing.
Crossing my fingers we do find out more details at the 2/3 hearing.