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 (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".