Melissa was elected as the federal member for Fremantle in the November 2007 election that marked the beginning of the new Rudd Labor Government. Before entering parliament, she worked as a senior lawyer in the United Nations – with the UN peacekeeping mission in Kosovo, in Gaza to assist Palestinian refugees, and in the Office of the Under-Secretary-General for Management in New York where she was responsible for oversight of the internal system of administration of justice, as well for establishing the UN Ethics Office, including instituting programs for whistleblower protection, financial disclosure, ethics training and advice and standards of conduct. In 2006 Melissa took up a legal position in the UN International Independent Investigation Commission in Beirut, investigating the assassination of the former Lebanese Prime Minister, Rafik Hariri. At this time, Melissa also became the Deputy Chief of Staff of UNIIIC. Prior to joining the UN, Melissa was a lecturer in the law school at Murdoch University and, before that, the solicitor in charge at the Bunbury Community Legal Centre. It was in this role that Melissa's strong sense of a public service vocation was formed through her direct experience of working with people who could not afford private legal advice or representation.