Blackwell made her acting debut in 2008, guest starring in the TV drama Skins at the end of the second series. When Skins returned in 2009 for a third series, only she and Kaya Scodelario remained from the old cast. Thereafter, they were joined by a new cast for the third series, which premiered on 22 January 2009 in the United Kingdom. Blackwell's character Pandora Moon met Effy in school, and they became friends. In the third season, Pandora dates Thomas, a boy from Africa who works at their school.