Reiff is an agent of the D.E.O..
When Supergirl was fired from the D.E.O. for failing to reveal her secret identity, Colonel Lauren Haley decided to discover her identity in order to bend her to her wishes. For this, Haley interviewed most of the agents who had worked with Supergirl to get the most information about her. Alex Danvers asked those who know Supergirl's true identity to keep it to themselves, and they all agreed.
Agent Reiff was questioned and ultimately gave in, telling the truth to Haley, for which she apologized to Director Danvers. Shortly following, after the D.E.O. was attacked by the Morae, Haley sent forward Agent Reiff, only for her to be attacked by one of the Morae. Reiff, along with Alex and several fellow D.E.O. agents who knew Supergirl's true identity, had that fact erased from their mind by J'onn J'onzz with their consent.
The D.E.O. was called to investigate what appeared to be a meteorite or a space craft falling to Earth; Reiff continued the investigation as Director Danvers talked with Haley. Reiff called the women to see her findings, that something had removed the heart of a person and left his body behind.
Agent Reiff accompanied Alex as the D.E.O. rushed into the office of Lena Luthor and found her unconscious but alive. While Alex checked on Lena, Reiff observed that there was a letter on the desk; she handed the letter made by Lex Luthor to her supervisor and observed Lena until she awakened.
During the Anti-Monitor Crisis, Reiff as well as everyone in the multiverse except for the seven Paragons, was killed in an antimatter wave by the Anti-Monitor on December 10, 2019, only to be restored a month later, after the Paragons and the Spectre created a new universe.
Reiff brought Brainy files and information on people and organizations that denounced people who were transgender.