KISS theory: AW was pregnant in July, thought the baby would save her failing marriage, she miscarries but tells no one and begins plotting to locate a replacement baby.
She finds AB, a prolific poster on community help and support pages, lures AB, murders her, attempts to pass AB's baby off as hers that she just gave birth to.
AW even went so far as to take the placenta she just ripped from the dead or dying AB's womb and shoves it into her own pants. She then meets emergency personnel at a local business parking lot (because she can't have them come to her home because - dead body to explain) and pretends she has just given birth to a stillborn AB's baby. She refuses all medical treatment because she did not give birth and it will be immediately evident to medical professionals.
I have to wonder if the baby would have made it had it received medical attention immediately rather than being dragged from it's mother, it's abductor's home and off to that parking lot. AW is the worst sort of evil. MOO