Chaffin was born and raised in Newton, Massachusetts. She is a regular performer at the Upright Citizens Brigade Theatre in Los Angeles, often performing with her comedy partner Jamie Denbo. She has done many guest voice appearances on Nickelodeon animated programs. From 2008 to 2009, she worked with Amy Poehler as a writer and voice actor on the animated series The Mighty B! playing several roles, including that of Portia's cousin, Chelsea. Chaffin is also known for playing Coco Wexler, the girls' dorm adviser on all four seasons of Nickelodeon's Zoey 101.