Doppelganger (1993) on Netflix

A writer with a room for rent acquires a strange new roommate with a psychotic alter-ego that follows her wherever she goes.

A woman moves from NYC to LA after a murder, in which she is implicated. She is followed by what is apparently her evil alter- ego. She moves into a room for rent by a writer, and he begins having an affair with her, but after some strange things happen, he's not so sure if the affair is with her or her doppelganger.

—Ed Sutton <esutton@mindspring.com>

Holly Gooding moves from New York to Los Angeles to visit her brother in a mental institution and rents the room of the aspirant writer Patrick Highsmith, who needs money to be not evicted. Soon they have a brief affair but the erratic behavior of Holly intrigues Patrick. He learns that she is followed by her doppelganger, and she has discussed the subject with her psychiatrist Doctor Heller. What is happening to Holly? Does she have also a mental problem? Does she have a doppelganger?

—Claudio Carvalho, Rio de Janeiro, Brazil