I'm not professing to know the mind of this demon, you are. I see only a calculating multiple murderer who should get the needle.
If, as has been asserted, she is going to be on drugs and doing the "thorazine shuffle" on the cold, hard tile of an institution floor for the rest of her life, what purpose is served by treatment? The death penalty is appropriate here.
If you were sick, would you not be entitled to treatment? That's what we do in civilized societies, we treat the sick.
Anything else is taliban stuff. The taliban certainly would see it your way about killing the sick as a matter of principle and righteousness.