And mentally disturbed she was. Her mental illness was well documented long before she killed her five children. If you want to talk about evil, I think a strong example is her husband, Rusty Yates. He knew after the second baby that she should never have another child because she experienced the most extreme (5%) post-partum depression a woman can have.
Curiously, when she delivered her last baby, the little girl, and her father died and she attempted suicide, Rusty Yates did not take her to her psychiatrist of record. Instead, he took her to a doc-in-the-box. She was catatonic, but once she was able to grunt a "Yes" or "No," she was released AND taken off the one medication that stopped her hallucinations. Less than two weeks later, all her children were dead, drowned to save them from the eternal damnation Andrea Yates was sure her poor mothering would doom them to.