Dr. Shein is the hidden secondary villainess from "Don't Stay Up Late", the 2nd book in R.L. Stine's revived Fear Street series (published on April 7, 2015).
She was a therapist and the friend of main villainess Brenda Hart. She was involved in Brenda's plot to raise a demonic creature, sending her teenage girls under her care to babysit Harry (the half-human creature they had successfully created). Prior to the events of the book, Dr. Shein had Brenda's previous babysitter Joy Fergus placed in a mental hospital after she found out Harry's secret. During the book, Dr. Shein became the therapist to protagonist Lisa Brooks, who was sent to her after she was involved in a car accident that killed her father and left her with brain trauma. She had her become Brenda's new babysitter and acted as support when she began seeing Harry in his demonic form, saying it was just the result of her traumatized mind and giving her a medical prescription.
Dr. Shein's villainous reveal came after Lisa discovered Brenda's evil secret and barely escaped. She at first acted as though she were going to help Lisa--but then revealed she planned to have her sent to a mental hospital to protect her secret, blaming the murders Harry committed during the book on Lisa for disobeying Brenda's order to not let him stay up late. But at that moment, Lisa revealed that she had secretly had Facetime opened on her phone, and the people she had on the call were Shadyside detectives that were waiting in the lobby. Dr. Shein attempted to flee, but was stopped by the detectives and arrested.