Question: Which character created by Grant Morrison and Frank Quitely did Brianna Hildebrand play?

Context paragraphs:
Riot at Xavier's: "Riot At Xavier's" is a four-part storyline that ran from New X-Men #135-138 (2003).  It was written by Grant Morrison and features artist Frank Quitely's last work on the title.  The story centers on an original character of Morrison's, the teenage mutant Quentin Quire.  According to Morrison, the storyline was inspired by a playground riot he witnessed in his youth.

Quentin Quire: Quintavius "Quentin" Quirinius Quire, also known as Kid Omega, is a fictional character appearing in American comic books published by Marvel Comics, usually in those featuring the X-Men.  A green-skinned character resembling Quire appeared in one panel of "New X-Men" #122 (March 2002), and appeared colored pink on the cover of "New X-Men" #126.  Quire appeared in his now-familiar, canonical form in "New X-Men" #134 (January 2003).  He was created by writer Grant Morrison and artist Frank Quitely.

Brianna Hildebrand: Brianna Caitlin Hildebrand (born August 14, 1996) is an American actress.  She is known for appearing in the web series "Annie Undocumented", and as Negasonic Teenage Warhead in the 2016 film "Deadpool".

All-Star Superman: All-Star Superman is a twelve-issue American comic book series featuring Superman that was published by DC Comics.  The series ran from November 2005 to October 2008.  The series was written by Grant Morrison, drawn by Frank Quitely, and digitally inked by Jamie Grant.  DC claimed that this series would "strip down the Man of Steel to his timeless, essential elements".

Cassandra Nova: Cassandra Nova is a fictional supervillain appearing in American comic books published by Marvel Comics, most commonly in association with the X-Men.  Created by writer Grant Morrison and artist Frank Quitely, Cassandra first appeared in "New X-Men" #114 (July 2001).  Cassandra is a "mummudrai," a parasitic life form born bodiless on the astral plane.  The mummudrai that became Cassandra became telepathically entangled with the future Charles Xavier, who possesses vast mutant telepathic powers.  This granted Cassandra some psionic powers herself, including the ability to exit the womb and create a body.

Tattoo (comics): Tattoo, later Longstrike, is a fictional mutant character in the Marvel Comics Universe.  Her first appearance was in New X-Men #126, created by Grant Morrison and Frank Quitely.

Negasonic Teenage Warhead: Negasonic Teenage Warhead (real name Ellie Phimister) is a fictional character appearing in American comic books published by Marvel Comics.  The character was created by Grant Morrison and Frank Quitely, and named after the song "Negasonic Teenage Warhead" by Monster Magnet.  The character is a mutant who displays telepathic and precognitive powers, and is a student of Emma Frost.

Jupiter's Legacy: Jupiter's Legacy is an American superhero comic book series, first published in 2013, written by Mark Millar, drawn by Frank Quitely, colored and lettered by Peter Doherty and published by Image Comics.  Published as a series of eponymous limited series and interstitial prequel limited series, it is to date the longest series that Millar has published as part of his Millarworld line of creator-owned comics, spanning an issue run three times as long as his then-most recent series, "Super Crooks" and "Nemesis".  It is also the first collaboration between Millar and Quitely since their work on "The Authority" in 2001, and Quitely's first long-form work with a writer other than Grant Morrison.

List of Marvel Comics characters: U: Ugly John is a mutant in the Marvel Universe.  The character, created by Grant Morrison and Frank Quitely, first appeared in "New X-Men" #114 (July 2001).

Phaser (comics): Christian Cord codenamed Radian and later Phaser is a fictional mutant character in the Marvel Comics Universe.  His first appearance was in New X-Men #135, created by Grant Morrison and Frank Quitely.

Supporting paragraphs: Brianna Hildebrand Negasonic Teenage Warhead
Answer: Negasonic Teenage Warhead