this is one of my least fave episodes....and full of "holes" as you describe Irene...plus the Celeste Holme character passing out is simply too over the top for me....
I do however like the "tone" of the episode and Joyce Van Patten plays the character with fine restraint...
I just watched this yesterday, and my two takewaways were "no gunshot residue on either victim's hands", and didn't make sense she would implicate the Neice, who she seemed to care for dearly, "like her own daughter" she said.