https://www.google.com/amp/s/www.redstate.com/elizabeth-vaughn/2020/03/31/remember-the-woman-who-fed-her-husband-fish-tank-cleaner-and-he-died-turns-out-theres-more-to-it/amp/
According to this news article the woman had a history of mental illness, so she was clearly not in her right mind. There is also evidence to suggest that it is even possible this was an attempted murder? She had previously said she wanted to divorce her husband.