Speculation
Seriously Injured Sunday night- cover up plan goes into motion.
Mon - plan is executed. She takes a trip with G. Isolated area is somewhat randomly picked where you can hide in broad daylight (search area). Realization of wearing Apple Watch after returning causes an ‘OH NO’ moment after reporting G as a runaway. House is cleaned, but leaves traces. Plan for retrieval goes into motion for the next day - she has to move him because her watch will soon lead them right to him.
Tues - retrieval plan with rental car is executed in daylight after dropping off husband, but leaves traces of evidence both at the search area and in the car allowing for a tampering with a deceased body charge. Tues drive away...
Weds- rental car is driven back from who-knows-where, after main evidence is buried. Car is cleaned and returned, but leaves evidence.
This leaves the home with traces of serious abuse, possible witnesses of abuse (little sister & older sister), a trail to the search area and vital signs on the Apple Watch, physical evidence at the search area tying her to the scene, and physical evidence tying her and G to the rental car.
This is just a possible scenario which would seem to point to her. Probably way off track, but I wonder if all of that would be enough to bring charges like first degree murder. There’s got to be more. Lots more.