Harriet has served a distinguished career at the United Nations, including as scheduling officer for three Presidents of the General Assembly, during the 71st, 72nd, and 73rd Sessions.  She has also served in the Executive Office of the Secretary-General for four Secretaries-General, Javier Perez de Cuellar, Boutros Boutros-Ghali, Kofi Annan, and Ban Ki-moon. She was an assistant to the Deputy Secretary-General Asha Rose Migiro and to Secretary-General’s Special Adviser on Climate Action and Just Transition. 

Harriet started working in the United Nations in 1985, in the Press Section of the Department of Public Information, moving on later to the General Legal Division of the Office of Legal Affairs, where she worked as an administrative assistant until 1991. She has served in UN Missions in Geneva on the Yugoslavia peace process for Martti Ahtisaari Cyrus Vance and Lord David Owen and for Lebanon for Mr. Staffan de Mistura, the Personal Representative of the Secretary-General, among others.