To me, the scene alone says that this was some sort of weird accident and not murder.
You have a bloody mess in the basement, but no footprints from a killer, and no other trace of a third party whatsoever.
You'd expect a killer to make sure she was dead, and not give her the opportunity to apparently stand up at the bottom of the stairs.
You'd expect more severe internal injuries, and for that to be the cause of death as opposed to external blood loss.
I think she was maybe having balance issues, struck her face, tumbled to the bottom of the stairs, and as a result, wasn't thinking clearly (like climbing the stairs for help).
I remember the Peter Porco murder case, where after being attacked in bed with an axe, he woke up and went through his morning routine, making lunch, writing a check, and doing the dishes when he finally succumbed.
His injuries were much more severe, and included massive brain trauma, but it wouldn't surprise me if her blood loss caused her to act irrationally.