There are still too many wildly varied scenarios.
A good shot, CPL holder, firearms familiar, smart adult, won't often crank a bunch of rounds through a window 8' up, in to the darkness. I'll check again for an outdoor light, but the "shot one in the face" comment is puzzling. Shooting in an enclosed room is really loud, disorienting, and muzzle flash messes with your eyesight. In high stress situations, fine motor skills go to heck. Messing with a cell phone while in likely her only gunfight, seems suspect. If the ceiling round was from her gun, and all the window shots were from inside, I doubt the "2 guys" existed.
Cougar is irrelevant, or alibi-builder.
Same with staying alone. I know people who would pay for desolation like that, to read, decompress, re-center, whevs.
AQ and BF fuel stops, full phone records, better timeline of known/stated/speculated movements, before and after LE arrived, would really help.
IMO:
Altered state of consciousness, she ran out in the woods and hid or dropped from exhaustion/exposure. The recent discovery of a teen boy after 4 years, in a park far smaller, that had been searched several times, and the terrain up there, give me little faith in the attempted searches done.
Distant second:
BF carried out a far more complex murder than seems reasonable. He may have, in sis's words, been "taking care of" the baby sister, I don't get a shining armor vibe about him. The complicated and bizarre storyline would be more likely if he was psychotic, or had at least another involved. Half-joking, I long ago surmised that 2 half-wits don't add up to a full mind, but that you have to multiply the fractions for an ever shrinking chance of getting away clean. Canadian First Nation murder recently, springs to mind.