She starred as Natalie Green in the sitcom The Facts of Life from 1979 to 1988, and is known for voicing Velma Dinkley in the Scooby-Doo franchise from 2002 to 2015.
Cohn was born in Los Angeles, California, and was raised Jewish. Cohn is unmarried and has no children. She is also a strong supporter of the LGBT community and has stated that she is proud to be a “fag hag.”
She has a degree in cultural anthropology from Loyola Marymount University and is a founding member of the weSpark cancer support center.