She's crazy as an crap house rat. Unfortunately, our legal system doesn't deal with crazy folks very well nor does society, since she was still allowed to run around nutty until she did something heinous.
Perhaps, one day when we have the technology to specifically identify most diseases in the brain that will change.
If your psychosis makes you dangerous, then the relevant point isn't your psychosis, it is the fact that you are dangerous.
If you intentionally kill people who are no threat to you, your life should be forfeit. What craziness boils down to is lack of a good motive, a moot point.