Born to athletic parents with backgrounds in collegiate swimming and professional American football, Stephens was first introduced to tennis at the club across the street from her house in Fresno, California. Her stepfather was a competitive recreational tennis player and served as her primary inspiration for beginning to play the sport. Stephens moved to Florida to train at a tennis academy, ultimately working with Nick Saviano for many years. She developed into a promising junior player, reaching a career-high ITF junior ranking of world No. 5 and winning three out of four Grand Slam girls' doubles titles in 2010 alongside her partner Tímea Babos.