Susan Lyle is a character from Supernatural The Animation.
Susan's husband and son died in an accident. Some time after, she met John Winchester and helped him take care of his children. Susan grows exceptionally fond of Sam, due to the similarities between him and her late son, since they would have been about the same age.
Dean is reluctant to accept her, while Sam grows increasingly fond in return. John also finds her presence a necessary comfort for his sons.
However, after a hunter attacks their home and tries to hurt Sam, Susan decides to kidnap Sam and take him to a scrapyard, where she expresses her wish to be with him forever. It is then revealed that Susan had made a deal with Azazel in exchange for the return of her family.
Dean pursues her and begs Sam to return to him, which Sam chooses to. Susan is visibly hurt by this, but ultimately decides to rescue the boys at the cost of her own life, by attacking the contraption which was under demonic possession.