Regardless of what the letter of the law might say about this particular incident I would give her the benefit of the doubt...unless,perhaps,there's an important point here that I'm missing (which seems possible).
“A normal,decent,person isn’t gonna behave entirely normally or rationally in the seconds (or even minutes) after having been attacked with a firearm.”
I agreee. She’ll walk.
Simple solution. When the other perp resumed the offensive the lady with the firearm yelled, “Stop or I’ll shoot!” Doesn’t really matter if anyone heard her. That is what she said...or that is what she said she said.