Supernatural season 3 explains how Mary's friends from The Winchesters spinoff died. The spinoff premiered in 2022, following Mary and John as well as their friends, who never appeared in the original series. In season 3, Sam discovers that all of Mary's family, friends, and acquaintances were killed by Azazel, who had made a deal with Mary and claimed Sam as one of his "special" children.
This explains what might have happened to her friends in the original timeline. The Winchesters changes the characters' futures, as it creates an alternate timeline. The past events established in Supernatural don't matter in the spinoff, giving future storylines more freedom.
