Jen was born and raised in Fresno, California, and graduated from Vassar College with an Bachelor of Arts in English, and followed that with a Master of Arts in Folklore Studies & Literature from the University of Oregon. Jen diverged from the Ph.D. track and began pursuing a career in comics, her first published work was a story in the 1998 Dark Horse Presents annual that saw the first appearance of Buffy the Vampire Slayer in comic book form.

Jen's first major writing gig in comics was the Oni one-shot set in the world and sharing the name of The Blair Witch Project, along with the follow-up series The Blair Witch Chronicles. Her work with Oni led to the creation of Hopeless Savages, featuring members of the Hopeless-Savage family, parents hailing from the 70s era of punk and their offspring, who have carved out their own cultural identities. The first four-issue series was nominated for an Eisner Award for best limited series in 2002, a Friends of Lulu Award in 2003, and was chosen as a 2004 Popular Paperback for Young Adults by the American Library Association. The original mini-series was followed by two more four-issue minis, Hopeless Savages: Ground Zero and Too Much Hopeless Savages.

Jen's work at Oni led to other series at DC, including the mini-series El Ciclo and Year One, and at Marvel, where she's currently writing a mini-series featuring Black Cat. In addition to her Marvel work, Jen currently writes the Liberty Belle & Hourman back-up series in JSA All-Stars.

Jen lives in Oregon with her husband and two children.