During this period, Hannah read Personal History, the 1997 autobiography of The Washington Post publisher Katharine Graham. Her then-boyfriend (now husband) challenged her to write Graham's story as a film.

Hannah did her undergraduate studies at the Pratt Institute in New York. Following an internship on 2007's Reign Over Me, she was admitted to the AFI Conservatory, in the producing discipline.

In October 2016, Hannah sent the finished script, titled The Post, out to agents, with the hope of finding representation. On October 28, she received a call from Producer Amy Pascal, the former chair of Sony Pictures. The script appeared at number two on the 2016 Black List, an annual Hollywood survey of the 'most liked' film screenplays not yet produced. Pascal won an auction for the script soon after, and quickly enlisted Steven Spielberg, Meryl Streep and Tom Hanks as Director and stars, respectively.

It was announced on October 27, 2017 that Hannah's next project would be Only Plane in the Sky for MGM, based on a Politico article by Garrett Graff about the immediate aftermath of the September 11 attacks. She is also working on a miniseries titled Mercury 13 for Amazon Video, based on Martha Ackmann’s book The Mercury 13: The Untold Story of Thirteen American Women and the Dream of Space FLIGHT. The project reunites Hannah with The Post Producer Pascal and actor Bradley Whitford. Hannah would serve as showrunner and executive Producer should the show be ordered to series.

After graduating from AFI, Hannah moved to Los Angeles. She got a job in development at Denver & Delilah, Charlize Theron’s production company. Several years into her role, Hannah realised she didn't want to be a Producer and decided to write a film of her own, about 'a 70th-birthday party gone awry'. She sent the script to her boss and in 2012, based on the encouraging feedback, quit her job to pursue writing full-time.