Mewis grew up in Hanson, Massachusetts, where she attended Whitman-Hanson Regional High School and played on the soccer team. She finished her high school career with 74 goals and 34 assists. She was a three-time NSCAA All-American, three-time All-New England and All-Massachusetts team honoree and a three-time Eastern Massachusetts Girls Soccer Association Div. 1 First-Team All-Star. In 2008, Mewis was named the NSCAA Youth Player of the Year and the US Soccer Young Female Athlete of the Year. In 2009, she was named to the Parade All-America team.
