The fans analyzed the treatment of women in fiction and concluded that they are often killed or harmed to advance the narrative of male characters.

After Deadpool was canceled and relaunched as Agent X, Simone continued as writer, but eventually left the project after a conflict with the series' editor.

Simone moved to DC Comics, where she wrote Birds of Prey in 2003 from issue #56, which featured an all-female team: Oracle, Black Canary, Huntress, and Lady Blackhawk.

In 2005 Simone wrote the Villains United limited series – part of the Infinite Crisis crossover – starring Catman.

She also wrote a two-issue story arc that focused on Hawk and Dove for a rebooted Teen Titans series with Rob Liefeld as artist.

Other works by Simone include Action Comics, The Legion, Rose and Thorn, WildStorm's Gen13, and an Atom series based on ideas by Grant Morrison and penciled by John Byrne and Mike Norton.

She wrote a creator-owned project about a retirement community of super-heroes, Welcome to Tranquility, for WildStorm, and contributed to Tori Amos's Comic Book Tattoo.

[19] Simone introduced Alysia Yeoh, the first transgender character written in a contemporary context in a mainstream comic book.

Oni Press published her graphic novel Seven Days with art by Jose Luis in 2020 as part of an initiative to launch a new Catalyst Prime superhero universe.

[28] In Nightwing #110, Tom Taylor introduced a bear named in her honor, Gail the Slayer, as a tongue in cheek reference to their continued mock feud.

[30] In 2005, Simone wrote the Justice League Unlimited episode "Double Date", which featured Question, Huntress, Green Arrow and Black Canary.