Diane and her "golden child" Rachel, systematically carried out executions on members of their family, who they judged were unproductive and just plain annoying.

References:

Mother convicted of poisoning her family maintains her innocence - ABC News (go.com)

Antifreeze Murders in Missouri: How a Mom and Daughter Planned to Kill Family (people.com)

Jun 27, 2013, page A5 - The Springfield News-Leader at Newspapers.com

Missouri Woman Recalls Moment She Suspected Her Mom Tried to Kill Her - ABC News (go.com)