Madison is a character from Supernatural The Animation.
Madison was the assistant of Mulligan, a lawyer working at the DA's office. One night, Mulligan is killed by what appears to be a wild dog, though Sam and Dean Winchester correctly deduce that it's a werewolf attack.
During interrogation, Madison reveals she is having problems with her ex-boyfriend, who often suspected there was something between her and Mulligan. Sam, having grown attached to her due to the similarities between Madison and Jessica, promises to protect Madison whatever the cost.
Problems arise when Madison herself transforms into a werewolf and kills Kurt. Dean wants to kill her, but Sam chooses to find an alternative. They agree to hunt down the one responsible for biting Madison, but despite killing the werewolf, Madison remains unchanged.
Madison desperately wants to kill herself out of grief, but Sam stops her every time. Eventually, the brothers are forced to end her life when she attacks Dean. Sam is the one to shoot her.