As a child actor, Gertz was in one episode of "Diff'rent Strokes" along with Andrew Dice Clay. She also had a recurring role on "The Facts of Life" as Blair's friend and fellow schoolmate Boots St. Clair. Gertz made her film debut in the 1981 romance film "Endless Love", which was followed by a co-starring role in the 1982–83 TV sitcom series "Square Pegs". She gained more significant attention with a starring role in 1987's "Less Than Zero", as the friend of a doomed drug addict played by Robert Downey, Jr. She also starred in the 1987 film "The Lost Boys" as Star, the "half vampire" girlfriend, with Kiefer Sutherland and Jason Patric.