McClung, of Coupeville, Washington, was born and raised in Orange County, California, graduating from Mission Viejo High School before going on to attend the U.S. Naval Academy where she received her officer's commission in 1995. McClung competed as a gymnast in high school and in college. She was a triathlete (having competed in six Ironman competitions) and a marathoner. In October 2006, she organized and ran in the Marine Corps Marathon's satellite competition in Iraq.
In January 2006, McClung was deployed to Iraq as a public affairs officer with the I Marine Expeditionary Force (I MEF). In December 2006, she was in the final month of a yearlong deployment to Iraq.
On December 6, 2006, McClung was serving with the I Marine Expeditionary Force as the Marine Corps head of public affairs for Al Anbar Province, in charge of embedded journalists. Earlier in the day, she had been accompanying Oliver North with his Fox News camera crew in Ramadi. She subsequently was escorting Newsweek journalists into downtown Ramadi. A massive improvised explosive device (IED) destroyed McClung's Humvee, instantly killing McClung and the other two occupants. The Newsweek journalists were not injured.
Major McClung was the first female graduate of the United States Naval Academy to be killed in action since the school's foundation in 1845.
Major McClung was buried with full military honors in Arlington National Cemetery on December 27, 2006.