[8] As an undergraduate, Sullivan attended Brown University, where she majored in English language and literature and received the Francis Driscoll Premium Award from the Classics Department.

[10][11] Sullivan began her career with service in The Peace Corps, working in the Democratic Republic of Congo (then Zaire) from 1980 to 1983, teaching English in Mbanza Mboma.

When she embarked on a career as a U.S. diplomat, Sullivan returned to Africa, serving as a consular and political officer in Cameroon from 1986 to 1988.

Just before accepting the role as Ambassador, she served two years as Chief of Staff to the Deputy Secretary of State for Management and Resources.

[12] Sullivan was nominated to be the next ambassador to Ghana by President Donald Trump on July 9, 2018, and confirmed by the U.S. Senate on September 6, 2018.

Her nomination was favorably reported out of committee a third time on April 17, 2024, and was confirmed by the full Senate on June 20, 2024, by a 45–26 vote.