Madeline was the true main villainess In "The Slice Girls" from Season Seven of Supernatural. She was the leader of a group of powerful Amazons who has been killing men left and right. Madeline was played by Jill Teed.
The Amazon women would mate with these men, become impregnated, and give birth to baby girls who quickly emerged into their teenage years. Madeline later trained the teenaged offspring, one of them being Emma, to go out and kill their fathers.
Madeline instructed Charlene to kill the brothers, but she was killed herself by Sam, who later shot and killed Emma.
The fate of Madeline and the rest of the Amazons was unknown in the episode, but in the following episode, "Plucky Pennywhistle's Magical Menagerie," Dean revealed that the entire group (including Madeline) was wiped out.