Boyle was born in Davenport, Iowa, the daughter of Sally Boyle, a clerical worker, assistant, and manager. Although she is of mostly Roman Catholic Irish descent, Boyle also has an Italian-American great-grandfather. She is named after a character in Boris Pasternak's novel Dr. Zhivago. She was raised in Chicago, Illinois and Wisconsin. Boyle studied at and graduated from The Chicago Academy for the Arts.
Boyle's first film role was a bit part in Ferris Bueller's Day Off (1986), which earned her a SAG card, though her scene was eliminated from the final cut of the film. She then appeared in the mini-series Amerika (1987) and films Poltergeist III (1988) and Dead Poets Society (1989), before landing her first major part, that of Donna Hayward in the critically acclaimed series Twin Peaks. When the series ended in 1991, creator David Lynch produced a movie, Twin Peaks: Fire Walk with Me, but—largely due to her rise in fame and increased film offers—Boyle chose not to return. Moira Kelly took over the role of Donna for the film.
Boyle spent much of the 1990s making a name for herself in films with varying degrees of success. Some of her most notable roles during that time were: