Sergeant Major Smith-Leavy was born and raised in Kingston, Jamaica and enlisted in the Marine Corps in 1996 and underwent recruit training at Parris Island South Carolina. Upon graduation of recruit training, she reported to the School of Infantry for Marine Corps Combat Training in Camp Lejeune, North Carolina. She remained at Camp Lejeune where she attended Personnel Clerk's Course. Upon completion of MOS School, she was transferred to Headquarters Battalion, Marine Corps Base Kaneohe Bay, Hawaii. While serving with Headquarters Battalion S-1 as a Personnel Clerk, she was meritoriously promoted to Corporal. 

In March of 1999, Sergeant Major Smith-Leavy was transferred to Inspector Instructor Staff, Bronx, NY, where she served as Unit Diary Chief. In March 2001, she was transferred to Manpower Management Branch (MMSR-3), Quantico VA, where she served as a Unit Diary Chief and Platoon Sergeant. She received orders to Drill Instructor School in March of 2003 and successfully completed Drill Instructor School (DISC) in June of 2003. Upon graduating from DISC, she reported to Close Combat Instructor Course and graduated in July 2003. She was then assigned to Oscar Company 4th Recruit Training Battalion (4thRtBn) as a Drill Instructor. In May 2004, Sergeant Major Smith-Leavy was promoted to Staff Sergeant. After completing four platoons she was assigned to Instructional Training Company Support Battalion, Martial Arts Section. In July 2005, Sergeant Major Smith-Leavy was transferred back to 4thRtBn where she completed her tour as a Senior Drill Instructor in June 2006. 

In July 2006, Sergeant Major Smith-Leavy reported to Officer Candidate School, where she served as a Sgt Instructor, Physical Training Instructor, Martial Arts Instructor and Platoon Sergeant. While serving at Officer Candidate School, she was meritoriously promoted to rank of Gunnery Sergeant. In July 2008, she completed her second tour as a Drill Instructor at OCS and was transferred to 1st Marine Division. In August 2008, Sergeant Major Smith-Leavy reported to 1st Marine Division, where she was assigned to the G-1 as the Operations Chief. While serving in 1st Marine Division, she held numerous billets. She was selected to serve as Company First Sergeant for Communications Company in November 2008. In June 2009, Sergeant Major Smith-Leavy was selected to serve as an Individual Augment in Baghdad, Iraq, where she served as the Linguist Manager and Marine LNO for Multi-National Security Transition Command-Iraq (OIF). In August of 2010, she deployed as the Operations Chief and Linguists Manager for 1st Marine Division (OEF). 

In March 2011, Sergeant Major Smith-Leavy was frocked to the rank of First Sergeant and transferred to 1st Intelligence Battalion, 1st Marine Headquarters Group, where she was assigned to the Counterintelligence/Human Intelligence Company. During her two-year tenure with 1st MHG, she served as the Headquarters Company First Sergeant, and acting Sergeant Major. 

In February 2013, Sergeant Major Smith-Leavy transferred to Headquarters Regiment, 3d Marine Logistics Group Okinawa, Japan. During her two-year tenor with 3d MLG, she served as the Service Company First Sergeant and Food Service Company First Sergeant. In June 2015, Sergeant Major Smith-Leavy transferred to Marine Wing Communication Squadron 18, where she was later frocked to the rank of Sergeant Major and served as the Battalion Sergeant Major. 

In June 2016, Sergeant Major Smith-Leavy transferred to 4th Recruit Training Battalion, where she served as the Battalion Sergeant Major and was transferred in September 2018. 

In November 2018, Sergeant Major Smith-Leavy assumed the duties as the Battalion Sergeant Major for 1st Supply Battalion, 1st Marine Logistic Group and was transferred in September 2020. 

In September 2020, Sergeant Major Smith-Leavy assumed the duties as the Group Sergeant Major for Marine Aircraft Group 11, 3D Marine Aircraft Wing and was transferred in Nov 2022. 

Sergeant Major Smith-Leavy's personal decoration include Defense Meritorious Service Medal, Meritorious Service Medal with Gold Star in Lieu of third award, Navy-Marine Corps Commendation Medal with Gold Star in Lieu of third award, Joint Service Achievement Medal, Navy-Marine Corps Achievement Medal with Gold Star in Lieu of third award.