Melanie (Andrea Drepaul) was a villainess from "Gods and Monsters," episode 14.02 of Supernatural (airdate October 18, 2018). She was introduced as a woman who was encountered by villainous archangel Michael, who had been inhabiting Dean Winchester's body since the Season Thirteen finale.
Michael and Melanie engaged in a series of back-and-forth flirting, when Melanie suddenly turned heel by revealing herself as a werewolf, flashing fangs and wild yellow eyes. The villainess had been seeking out Michael, only for the archangel to reveal that he was looking for not only her, but her pack leader, Phillippe. After subduing Melanie, Michael revealed his plan to use his grace to enhance monsters to destroy the human race, with Philippe and Melanie agreeing to the plan.
Later in the episode, the evil Melanie appeared with a group of werewolves at an abandoned building where Bobby Singer, Mary Winchester, and Sam Winchester were located. The werewolves went after the group, who were stunned over their inability to take down the group with silver. Melanie's target was Bobby, who saw Sam behead one of the werewolves, leading to Bobby doing the same to Melanie, killing her instantly.