Just saw the Netflix UM episode focusing on this AA case, "Body in the Basement". It sounds like I'm in the minority here, but I 100% believe that this was a tragic, horrific accident. And, I don't believe foul play/a stranger in the house were involved at all. Here is my take on this. Obviously, this is all IMHO only:
It was proven that the husband had nothing to do with this, given that he had an alibi - i.e., he was out of town @ the time AA died.
I believe that AA was either impaired/disoriented due to the migraine & the drugs she took (for the migraine) & that this led to her tripping/falling down the basement steps....or, it's also possible she tripped on her dog. Her severe injuries were probably caused by her falling down the steep flight of steps. I have known of at least one case where someone did die from falling down their steps (resulting in a head injury), so this is absolutely possible.
Her clothes being in disarray could have been something she did herself due to her disorientation. I.e., the clothes being this way doesn't mean that someone else did this to her.
IMHO the dog not going down the steps to check up on AA is inconsequential. I agree it may have been spooked/scared due to the noise(s) caused by the fall; the smell of blood, etc. - i.e., apparently dogs have a far better sense of smell than humans.