Andrea isn't going to kill you because you decided you don't want to be involved with her anymore. She is only a danger if you are her child and she is unmedicated and responding to her delusions and auditory hallucinations. SO no, the average person does not have a threat from her. Jodi can kill you anytime for doing something she does not like and feel not a shred of remorse.
The legal definition of insanity (in a nutshell) is not knowing right from wrong at the time a crime was committed. Andrea Yates was not properly cared for mentally and was really unable to care for herself mentally. She could not get proper treatment on her own volition. SHe slipped through the mental health system cracks many times and her own husband was completely clueless to the signs of how sick she really was. She felt, due to a brain chemical imbalance, that her children were being taken over by Satan and she had auditory hallucinations telling her that she was a horrible mother and if she continued to raise them they would burn in hell.
Jodi has been evaluated psychologically and psychiatrically and found to be sane. She knew right from wrong on the day she killed Travis. Oh sure her ideas of right and wrong are backwards, but she shows signs of knowing what she did was legally wrong when she voiced concerns about herself and how her life was over. She has no brain chemical imbalance telling her that she had to kill Travis for xyz reasons. She knew clearly what she was doing that day.
Andrea Yates was found to been suffering horribly on that horrible day she killed her children, Post Partum Psychosis being one of many diagnoses. She was sentenced to live for the rest of her life in a state hospital. She gets her meds and therapy and is able to have a somewhat stable life. However she will never see life outside a hospital. This is where she should be. She is not capable of taking care of herself at all.
There are no meds to treat Jodi. Jodi is not mentally ill in the chemically imbalanced sense. She has mental issues sure, but not treatable by meds. Now she very obviously (IMO, since I am not a professional treating her or a licensed professional at all) has Axis II (Cluster B's) personality disorder(s) of some sort
http://behavenet.com/personality-disorder
A therapist can work with someone who solely has these but they are very very difficult to work with...because again it is something wrong in her personality, not her brain chemicals. The personality is the particular combination of emotional, attitudinal, and behavioral response patterns of an individual.
Jodi has no qualms about hurting anyone that wrongs her. She is far more of a danger than someone like Andrea Yates ever could be, because she knows exactly what she is doing, enjoys doing it, and would more than likely do it again if she could.
SO yeah, you can be sane and commit horrible crimes.