Fahn has three older brothers: Michael Fahn is a musician, while Tom Fahn and Jonathan Fahn are fellow voice and stage actors. In 2000, Fahn met musician Joel Alpers on the set of Vox Lumiere in Los Angeles, and they wed at Kauai, Hawaii in 2002.
Fahn is a member of the ensemble in the original Broadway cast of Stephen Schwartz's musical Wicked. In March 2004, Fahn played an understudy for Glinda, replacing Melissa Bell Chait who suffered a stroke. Fahn departed the show on October 31, 2004. She later became an original cast member of the Los Angeles sit-down productions, performing in the ensemble and again understudying the role of Glinda before departing on December 30, 2007.
In 2007, Fahn released her music album Avignon which was produced by her husband, Joel Alpers. The album also involved her brother Tom on trombone and sister-in-law Mary Ann McSweeney in bass. Alpers also played drums and percussion.
