Kirstjen Nielsen

Kirstjen Michele Nielsen (born May 14, 1972) is an American government official and national security expert. Nielsen was the 6th United States Secretary of Homeland Security from December 6, 2017 to April 10, 2019. Before, she served as Principal Deputy White House Chief of Staff to President Donald Trump from September 6, 2017 to December 5, 2017. She has informally performed the role of Deputy Chief of Staff since John F. Kelly became White House Chief of Staff on July 31, 2017.
Nielsen is the founder and former President of Sunesis Consulting.
On October 11, 2017, President Donald Trump nominated Nielsen to be the new United States Secretary of Homeland Security. On December 5, 2017, the Senate confirmed her nomination, by a 62-37 vote. She resigned on April 7, 2019.
Early life.
Nielsen was born on May 14, 1972 in Colorado Springs, Colorado. She was raised in Clearwater, Florida. She graduated from the Georgetown School of Foreign Service and earned a J.D. degree from the University of Virginia School of Law in 1999. Nielsen's mother is an italian descent while her father is a Danish ancestry.
Early career.
Nielsen served during the President George W. Bush administration as special assistant to the president and act as the senior director for prevention, preparedness and response at the White House Homeland Security Council. She also ran the Transportation Security Administration's offices of legislative policy and government affairs, a section she started. 
White House career.
Nielsen previously served as John F. Kelly's Chief of Staff at the Department of Homeland Security. She has informally performed the role of Deputy Chief of Staff since Kelly became White House Chief of Staff on July 31, 2017.
United States Secretary of Homeland Security (2017 – 2019).
On October 11, 2017, President Donald Trump nominated Nielsen to be the new United States Secretary of Homeland Security, replacing John F. Kelly. On December 5, 2017, the Senate confirmed her nomination, by a 62-37 vote.
Nielsen created the practice of separating parents and children accused of crossing over the U.S.–Mexico border illegally. Nielsen resigned on April 7, 2019, and Kevin McAleenan, the then U.S. Customs and Border Protection Commissioner, became Acting Secretary.
In a piece summarizing Nielsen's tenure at DHS, "Vox"'s Dara Lind wrote that Nielsen had been "arguably the most aggressive secretary in the department's short history".