I used to work in Pathology. It is very rare that there is only 1 cause of death. For example in her case its likely she suffered a heart attack and then fell down the steps. Or a stroke could have caused the fall. I read that lately she has had trouble walking, so its also possible she broke a hip and then fell down the steps.

Its too early to pick and choose what cause of death appeals to your narrative. The official report should state several causes that in combination caused her death.

Then too the chemical analysis takes about 6 weeks, so it could be as simple as too much wine.

They came out really quick with a reason; we dont even know if she had an autopsy.