Faber made her Broadway debut on December 26, 2005, replacing Stephanie D'Abruzzo in the musical Avenue Q. She played the big-hearted Kate Monster and the easy Lucy T. Slut. Starting October 30, 2006, she took a leave of absence from Avenue Q to appear as Clea in the Playwright's Horizon's production of Floyd and Clea Under the Western Sky. Faber returned to Avenue Q on December 19, 2006. Faber's last appearance in Avenue Q was on October 9, 2008.
Faber originated the role of Heather in the musical American Idiot while the show was being developed at Berkeley Repertory Theatre. She continued the role of Heather from the opening of its Broadway run until December 12, 2010.
She starred as Smitty in the 2011 revival How to Succeed in Business Without Really Trying alongside Daniel Radcliffe and John Larroquette, from the opening of the run until February 26, 2012.
Faber is married to the musician Gabe Witcher, best known for playing fiddle in the progressive bluegrass group the Punch Brothers since September 15, 2013.
