Of course she is insane, no one in their right mind commits murder. I think all murderers are mentally unstable. Murder isn't something "sane" people do.
They, of course, should be held accountable, but putting them with the general population of a state pen doesn't help anyonoe and will probably just result in further violence.
Insane criminals need to be medicated and treated in prisons for the criminally insane.
JMO
AM