Heather was born in Milwaukee, WI, on January 29, 1970, but soon moved to Springfield, VA where she attended North Springfield Elementary School. Her family moved often in her early years due to her father's job in the FBI. Just a few years later they Conejo Valley in California where she attended Sumac Elementary, Lindero Canyon Middle School, and Agoura High School. At Agoura, she got her first taste of acting, playing Dorothy in a school production of The Wizard of Oz, and remained so active in school theater that she was called a "theater geek" by her classmates and later voted "Most Talented" in her graduating class.
After graduation, Heather moved to Los Angeles where she soon broke into the movies, playing opposite Corey Haim in License to Drive and Drugstore Cowboy. In 1990 she won her first recurring television role as Annie Blackburn on Twin Peaks, a role which she reprised in the 1992 film Twin Peaks: Fire Walk With Me.
During this time, Heather attended the University of California at Los Angeles to pursue a Drama degree. While at UCLA she met, and became romantically involved with, actor James Woods, who helped her to be cast in his film Diggstown. She left UCLA after only two years, forsaking her degree in order to pursue acting full-time.
Heather stayed in the public eye for the next few years, playing notable bit parts including the role of the dream girl in Swingers, but her breakout role struck in 1997 when she was cast as "Rollergirl" in Boogie Nights. Two appearances in 1999 (Felicity Shagwell in Austin Powers: The Spy Who Shagged Me and Daisy in Bowfinger) cemented her into the spotlight where she has remained ever since.