Bertha Gifford was ahead of her time. She might have been one of the all time great women serial killers. She used arsenic. Oddly, she was also considered an outstanding cook.
One of my mother's older brothers was Bertha's hired hand in his teens. He lived on her farm and ate with her family. He was not poisoned.
You can read about Bertha HERE on Wikipedia.
You can read more HERE, including what happened to her. Be sure to read to the last sentence!