In the closing scene, when discussing the "posh" word for murdering of various relatives etc, murder of a sister is said to be fratricide when in fact this is the murder of a brother. To murder a sister is sororicide. (From the Latin "Soror" meaning sister.)
According to merriam-webster.com/dictionary/ Fratricide: one that murders or kills his or her own brother or sister or an individual (such as a countryman) having a relationship like that of a brother or sister.