What does the Bible say about people with mental illness?
Have a friend in Christ who is black/white; all are responsible for their actions all the time. "Mental illness" is a modern construct that is not Biblical. Saul, etc. suffered due to their sin.
Suspect her point confuses the "I'm sad, need some excitement so I'll shoot somebody" with "I don't want to live anymore 'cause everyone hates me."
If a schizophrenic purposely quits taking meds and then hurts someone--yeah I think they're culpable. If they hurt someone before they're diagnosed, then I don't think they should be held criminally liable.
Depression, for me, is a bit trickier.
Crux (IMHO): Does the Bible support idea that some mental illness is NOT sin and is there a circumstance when a person is not responsible for their actions (outside of knowlingly creating an altered state of being i.e. drunk, taking drugs, etc.)?