McGuire grew up in Missoula, Montana, in a military household as the oldest of six children.[1] Her father served 30 years in the United States Army Reserve.[1] McGuire graduated from Sentinel High School in 1975.[2] While in high school, she started in the Army Reserves.[1] She attended the University of Montana (UM), graduating in 1979.[3][4] McGuire was a radio/television major at UM and a member of the cheerleading squad, the school's Women's Rugby Club, and was a member of the Delta Gamma sorority.[1][5] Also at the university, she was involved in the Reserve Officers' Training Corps (ROTC).[2] McGuire was a member of the 279th Engineer Company at Fort Missoula through the ROTC Simultaneous Membership Program. At that time her father, William McGuire, was the first sergeant of the company.[6]
When the United States Disciplinary Barracks at Fort Leavenworth were re-opened in 2002, McGuire became the first woman in charge of the prison.[8][9] She went on to work as the assistant commandant of the United States Army Military Police School.[7] Starting in 2007, McGuire served 18 months as the provost marshal of the multinational corps in Iraq.[1] She was the first woman to serve as a provost marshal in the United States.[7] McGuire was also the senior advisor to the corps commander stationed in Baghdad.[9] In Iraq, she took fire while traveling by convoy and was there when a bullet passed through her barracks.[10] In 2008, she was promoted to the rank of brigadier general.[1][11] Also in 2008, she led the Army Suicide Prevention Task Force.[6]