Reed was born in Detroit, Michigan and was raised in Roseville, Michigan. She graduated from Roseville High School in 2003. She has one older brother named Corey and was raised in a conservative Catholic family, though she has also stated that she attended a Baptist church growing up. Reed studied dance from an early age and was dance captain in high school. While living in Detroit, she was an active member of her local community theatre and starred in the musicals Annie, Fiddler on the Roof and Grease. She attended Wayne State University and was a part of the Bachelor of Fine Arts program. She moved to Chicago and appeared in a number of local productions. In December 2008, she moved to Hollywood to pursue a screen career.
Since 2011, she has co-starred as Allison Argent, the female lead of the MTV series Teen Wolf. Before Season 3B of Teen Wolf, Reed wanted to move on from the show, do different things and explore other areas of film creatively. She approached executive producer of the show, Jeff Davis, who supported her decision. Reed left the show in March 2014 in the form of Allison Argent's death at the end of Season 3B.