Born in 1987 at Offut Air Force Base of military parents, Hallee started acting professionally at age 3 while her parents were stationed in Pensacola Fla. She had her first stage role at age 3, was discovered by agents, and immediately began booking commercials first in Florida and, soon after, in New York. She landed dozens of national TV and radio spots for such companies as Disney Cruise Lines, Jiff, Tyco, Burger King, Kraft, Hardees, Kellogs, and a one-on-one with Bill Cosby for Jello. Soon after arriving in NYC when she was 4-years-old, she landed a recurring role on the ABC soap, "Loving" (1983). TV and feature films followed with several Hallmark Hall of Fame TV movies before she landed One True Thing (1998), portraying a young Renée Zellweger and working opposite Meryl Streep and William Hurt. Next up was Tom Hanks's 8-year-old aunt in You've Got Mail (1998).
At age 11, she was nominated for her first Young Artist's Award for her chilling turn as a would-be child serial killer in the "Law & Order" (1990) episode, "Law & Order: Killerz (#10.2)" (1999). Showing dramatic range, that role was followed by a turn as a future nun in the independent feature, Manna from Heaven (2002). By age 12, she had moved with her family to Los Angeles where she immediately became a main go-to young actress for significant guest starring roles on network series while also landing leading roles in TV series pilots and made-for-TV movies. One of the finalists for "Lizzie McGuire" (2001), she was subsequently selected for the starring role in the Disney Channel TV Christmas Classic, The Ultimate Christmas Present. By age 14, she had landed a major recurring role on "ER" (1994), portraying Mark Greene's wayward daughter, Rachel. She continued with that series until its final episode in 2009, where her character was redeemed as a medical student following in her father's footsteps.
After "ER" (1994), she landed another major recurring role on "JAG" (1995), playing Harm's ward, "Mattie Grace Johnson". That was soon followed by a series regular role, playing "Daley" in the award-winning Discovery Kids, Flight 29 Down. During her teen years, she received several more Young Artist Awards nominations and two best actress awards. Other noteworthy film roles during her teens included playing Kristen Stewart's best friend, "Rachel" in Speak (2004), and a starring role opposite Richard Thomas, in Wild Hearts (2006) (TV), a Hallmark Movie Channel favorite. At age 19, she fought for and won the starring role in the independent feature, 16 to Life, garnering two best actress awards on the film festival circuit. This film was released on TV in February, 2011. In April, 2011, she starred in the independent feature, Right Next Door, opposite Linda Hamilton. While continuing with her award-winning acting career, she also made time to attend to her education and graduated in June, 2011 from UCLA with honors, Magna Cum Laude with a BA in Anthropology. She has lived in Beijing, China as part of her studies with UCLA and is fluent in Chinese.