Snyder was born in Glendora, California, to Lynda Lou (née Wilson) and Harry Guy Snyder. She is of Dutch descent on her father’s side. When she was 12, her parents separated and she moved with her mother to the small town of Shingletown, California, where she lived on a ranch and graduated from Redding Christian School, a private high school in Palo Cedro, California, that her parents helped found. Her parents eventually divorced in January 1997. She has two older half-sisters (Traci and Teri) through her mother. Traci is married to former In-N-Out President and current COO Mark Taylor. Snyder’s uncle Rich died in 1993 in a plane crash, and her father died in 1999 from an accidental drug overdose.

During 2006, Snyder and In-N-Out were embroiled in a bitter lawsuit with a former company executive, Rich Boyd. Boyd was fired for allegedly misusing company funds, but he claimed that Snyder, and then Vice-President Mark Taylor, were trying to oust the elderly Esther Snyder from the company. Both Lynsi Snyder and Mark Taylor denied the claims, and the lawsuit was settled out of court in May 2006.

On January 1, 2010, Snyder became the 6th President of In-N-Out, succeeding her brother-in-law, Mark Taylor, who was appointed the Chief Operating Officer of the company. She occupies the same position that her grandfather Harry (1948–1976), uncle Rich (1976–1993), father Guy (1993–1999), and grandmother Esther (1999–2006) previously held. Before Snyder became President of In-N-Out Burger, a taped message from her was broadcast to all company associates letting them know about the transition and the future of the company. Esther Snyder’s signature was finally replaced with Lynsi Snyder’s on associates’ paychecks in 2009, three years after Esther Snyder’s death.

In August 2012, Snyder reportedly purchased a 7-bedroom, 16-bathroom mansion with 16,600 square feet (1,540 m) of interior space in Bradbury, California, from Texas Rangers third baseman Adrián Beltré for a sum in excess of US$17 million. Snyder has stated that she works primarily out of the Baldwin Park office, home of In-N-Out University and formerly company headquarters, rather than the Irvine corporate headquarters because it is closer to her Bradbury home.

In February 2013, Snyder was ranked a billionaire for the first time by the Bloomberg Billionaires Index, based on an In-N-Out valuation of $1.1 billion. That same year, she ranked #93 on Maxim’s annual Hot 100 list.

Snyder is a devout Evangelical Christian, and has spoken several times about her faith. In 2015, her testimonial was featured on I Am Second. In it, she spoke about the many deaths within her family and her previous failed marriages and how her faith helped her cope with these misfortunes.

Like her father, Snyder is an avid drag racing fan and member of the NHRA. She regularly competes in drag racing events. In 2015, she was featured on an episode of Jay Leno’s Garage, where she showed off a modified ’41 Willys that was previously owned by her late father.