YES SNOKKUMS, You have hit on the scenario that I have always believed in.
I have discovered long ago that Borden Scholars are very passionate about their theories and convictions about who killed Andrew and Abby.
I have always believed that, though she did not swing the axe, Lizzie planned the killings. Though I think things probably did not go the way she had planned------or perhaps it did.
That is why she was in the Barn. Though she knew, and probably saw her dead stepmother laying on the floor, when it came to killing her father she could not bear being in the house while it was being done. I believe that killing her father was probably part of the "emotional Frenzy" (as Victoria Liincoln suggested, in a sort of "fit") or the heat of the moment when everything went wrong, for Andrew, that is. Sort of a murderous fever. I believe she wanted Abby dead, and even perhaps her father, and thus had hired someone to do it-------thus the reason no weapon was ever found or spatter of blood on her clothing. It is hard for me to believe that, at the very least, one solitary tiny blood drop did not hit her. That she could dispose of the axe so quickly.
It just happened too fast. If she had done it all, some evidence would have been discovered. Though the police did not have the crime technology they have today, I need to believe that they could not have been "that" incompetent---------or could they?