Alexander was born in Greenville, South Carolina, and moved to Grapevine, Texas when she was four years old. She is the only girl in a family of five children. Alexander first got into acting in grade school, where she took theater for fun. Alexander stated that she was actually kicked out of theater when she was in high school because she could not sing, so she instead went into sports. When she was 17, she substituted for a friend at a meeting with a scouting agency and she met her manager, Randy James, who sent her some scripts. After her graduation from Colleyville Heritage High School, a year and a half later, she moved to Los Angeles to pursue acting.