The following information was taken from the Sadie Swenson page on the Scream Queens Wiki.

Sadie Swenson, also known as Chanel #3, is one of Chanel Oberlin's minions, and formerly a member of Kappa Kappa Tau. As of The Final Girl(s), she was serving a life sentence at the Palmer Asylum of the Insane, along with Chanel Oberlin and Chanel #5, after Hester Ulrich incriminates them for being the Red Devil. She, and the rest of the Chanels, are soon released from the asylum and are now studying to be doctors at Cathy's hospital.