She is best known for her portrayal of Suzy Bannion, the protagonist of Dario Argento's cult classic Suspiria (1977),[2] and appeared in a supporting role in Luca Guadagnino's 2018 remake.

[3] Her other films include Stardust Memories (1980), Shock Treatment (1981) (the follow-up to The Rocky Horror Picture Show in which she replaced Susan Sarandon as Janet Weiss), Pennies from Heaven (1981), The Blue Iguana (1988), Safe (1995), Minority Report (2002), Bones and All (2022) and Nightbitch (2024).

[4] She attended the North Shore Country Day School in Winnetka, Illinois, and Sarah Lawrence College in New York.

Harper married Tom Rothman, a top executive at Sony Pictures (formerly of 20th Century Fox) on March 11, 1989, in an ecumenical ceremony.

[10] In a blog post on her official website in 2017, Harper revealed she had suffered from neovascular macular degeneration for the past 15 years, and that she receives injections in her eye every six weeks to treat the condition.