Edmondson is the middle daughter of comedians Adrian Edmondson and Jennifer Saunders. She grew up in Devon with an elder sister, Ella, and a younger sister, Freya. During her second year at the University of Manchester she decided not to audition for the Drama Society and, instead, formed a comedy group with four female friends. They appeared at the following Edinburgh Festival. After years working the comedy circuit with the all-female Sketch troupe, which they named Lady Garden (and later reformed as Birthday Girls with Rose Johnson and Camille Ucan) she broke through into television in 2008. She made her début in the Ben Elton sitcom The Wright Way, which was axed after one series.
Her role in the 2015 six-part BBC Three series Josh was singled out by The Independent newspaper as "very watchable", saying her "comic timing stuck out". The show's second series was broadcast in 2016, with a third broadcast in October 2017.
