The native New Yorker had already made her mark as a child performer, dancing for eight years (1968-76) with the American Ballet Theatre, and author with the children's book "She Was Nice to Mice" (McGraw-Hill, 1975). The success of the book brought requests from various publications (The New York Times, Village Voice) and while on a promotional tour, Sheedy was approached about acting. At age 15, she made her debut in TV commercials with a spot for Burger King and for the next three years, she alternated between commercials and Off-Off-Broadway productions.
Moving to L.A. to attend USC, Sheedy began to land roles in TV-movies and specials ("The Best Little Girl in the World" ABC, 1981; "I Think I'm Having a Baby" CBS, 1981). She first gained attention as a teasing Catholic schoolgirl who catches the attention of one of the cops on the NBC series "Hill Street Blues" (1983). That same year she made her film debut as Sean Penn's loyal girlfriend in the delinquent youth drama, "Bad Boys", and co-starred as Matthew Broderick's friend who becomes entangled in "WarGames". Sheedy went on to play one of the detentioners in "The Breakfast Club" and Gene Hackman's daughter in "Twice in a Lifetime" (both 1985). She displayed her comic abilities as a Cinderella-inspired character in the little-seen "Maid to Order" (1987) and as Molly Ringwald's cop sister in Alan Alda's "Betsey's Wedding" (1990).
Sheedy's feature output slowed somewhat in the 90s as the quality of her vehicles declined. But she rebounded with a strong turn as a fortyish photographer coping with addictions who falls in love with a young magazine staffer in the acclaimed indie "High Art" (1998). Building on her renewed credibility in the indie world, the actress offered terrific turns as lovelorn women in "Sugar Town" and "I'll Take You There" (both 1999), displaying a sexy charisma and off-kilter comic presence. Her much-touted return to the stage, however, as the first female to undertake the lead role of the German-born transsexual rock singer in "Hedwig and the Angry Inch" in late 1999 proved ill-fated. Still, her career resurgence continued into the new millennium with the lead in the Americanized "The Governor" (TNT, 2000), Lynda LaPlante's reworking of the British series about a female prison warden.