A screenplay by Forrest about the late musician Jeff Buckley, Becoming Music, was bought by Brad Pitt’s production company Plan B Entertainment in September 2000. In 2009 her screenplay LIARS (AE) was bought by Scott Rudin at Miramax, with Richard Linklater attached to direct. In 2009 she was listed on Variety’s “Top Ten Screenwriters to Watch”. Other screenplays in development:Know Your Rights (Film4) and How Could You Do This To Me (Paramount Pictures).

In 2001 Forrest contributed to an anthology on the writer J.D. Salinger titled Love & Squalor, with an essay describing Salinger’s influence on some current young writers. In 2007 she co-wrote and edited her first non-fiction book, Damage Control – Women on the Therapists, Beauticians, and Trainers Who Navigate Their Bodies, which was an anthology of essays of the emotional pain women suffer for their own physical wellbeing. The book features contributions from many well-known women, including Helen Oyeyemi, Marian Keyes and Sarah Jones.

Forrest was in a relationship with actor Colin Farrell, whom she met in 2008. She refers to him in her memoir as “GH,” short for “Gypsy Husband.”

In June 2012, Forrest married Australian actor Ben Mendelsohn, who won notice in Animal Kingdom. They had one child together in 2014, and divorced in 2016.

Forrest has written four novels: Namedropper (1998), Thin Skin (2002), Cherries in the Snow (2005), and Royals, which was released in the UK on October 31st 2019.