Mary Mulligan

Bethany Stevens, better known as Mary Mulligan, is an antagonist from Scream Queens. She is was the president of Kappa Kappa Tau in the 90s. Bethany/Mary's actions are directly responsible for the series' events. It is also revealed later in the season that she was dating Wes Gardner, and that she is the mother of Grace Gardner.

She is portrayed by Anna Grace Barlow.

History
Bethany is first seen in the Pilot when her friend Amy comes to her with blood on her hands. Bethany investigates, and learns that her friend Sophia Doyle is having a baby. While she originally shows (some) concern, the song Waterfall by TLC comes on, and Bethany says that Sophia bleeding profusely isn't worth missing the song. She then returns to the party, and convinces the others to do so, leaving Sophia to die in the bathtub.

Later, after Bethany returns to the bathtub, she finds Sophia dead and tells the others. Dean Munsch and Agatha Bean however, don't want bad publicity to the University, and shoot down Bethany's idea to call the police, saying she could go to jail for negligent homicide. So the five of them bury Sophia in the woods and give all of the girls, including Bethany, new identities. Bethany's new name is "Mary Mulligan" and she parts ways with the others.

More of Bethany/Mary's history is revealed in the episode "Mommie Dearest" when Chanel hires two personal detectives to investigate who the killer is, they show her a file that contains information about Grace's mother. Chanel reveals to Grace that Bethany hooked up with Wes on the night of the Kappa party when Sophia died. She got pregnant with Grace either that night or a few nights later. Bethany then disappeared using the alias Mary Mulligan to exempt her involvement in Sophia's death. Nine months later, Grace was born and that drove Mary off the deep end. She was arrested for shoplifting, petty larceny, grand larceny, drunk driving with a baby in her lap, drunk driving with a baby on top of her car, and possession of methamphetamine with intent to distribute. Wes then sued for custody of Grace and won. Mary died one year later after driving drunk and crashing into a tree, causing the car to burst into flames.

Trivia

 * She is very similar to Nurse Thomas, as they both chose to continue partying instead of saving someone else's life, causing said person's mentally ill families to seek vengeance by murdering in the same location.