Gemma joined Change.org in January 2016, assuming responsibility for the company's General Management globally. She was previously Executive Director of Crisis Action, having joined as the second member of staff in 2006, and led the organization to receive the 2012 MacArthur Award for Creative and Effective Institutions and the 2013 Skoll Award for Social Entrepreneurship.
In 2011, the World Economic Forum selected her as one of their Young Global Leaders. CNN named her as one of their inspirational women for 2014 and she became a Yale World Fellow in 2015. She previously worked for the Permanent Mission of the United Kingdom to the United Nations in New York, the European Commission and as a journalist.