Your last two scenarios seem the most likely to me, sadly.
I would like to know who dropped her off, where she took her vehicle, who her neighbors are, if she normally left her back door unlocked, had there been any deliveries, repairmen, etc. to the home, why her ID is missing... So many dang questions!
Has anyone looked at the property assessor's site? This house doesn't have a basement, does it?
Bob Ward Boston 25
MOO
ETA: And I wish they'd correct the NamUs entry. It still says her last contact was August 9.
The National Missing and Unidentified Persons System (NamUs)