She broke through in a guest starring role on an especially memorable episode of NBC's "Seinfeld", playing a relentless NYU student reporter who overhears Jerry and George in a conversation and misinterprets that they are a gay couple. Her resulting story "outing" them eventually becomes national news despite their protests. The episode was undoubtedly best known for the catchphrase "not that there's anything wrong with that", with which Jerry and George punctuated each denial, but Marshall proved her comedic talents and landed a series developmental commitment from NBC and several subsequent roles on the big and small screens. The Maryland native began her television career with guest shots on the series "True Blue" and "Mancuso FBI" (both NBC) and "The Flash" (CBS) in 1990 and "Dinosaurs" (ABC) and "Grapevine" (CBS) the following year. In 1992, she scored recurring roles in two ABC series "The Wonder Years" and "Life Goes On", playing a young divorcee in the former and an art gallery owner with an eye for HIV-positive painter Jesse in the latter. She followed her "Seinfeld" success with parts in TV-movies like "Nurses on the Line: The Crash of Flight 7" (CBS, 1993) and the thriller "Full Eclipse" (HBO, 1993). In 1994, Marshall starred on the short-lived Fox series "Wild Oats", a comedy following a group of twentysomethings and their romantic quests in Chicago.
She had marginally better luck starring as Jason Bateman's love interest in the Windy City-set "Chicago Sons" (NBC, 1997), although that sitcom too suffered an early demise. A recurring role as a love interest to Michael J Fox on the ABC sitcom "Spin City" followed later that year. During the 1998-99 season, Marshall starred opposite Jeremy Piven on the series "Cupid", playing a New York City psychiatrist and a man who believes he is Cupid respectively. While the program won critical notice and built up a core fan base, it failed to thrive in its various timeslots, and was unceremoniously canceled by the network just short of Valentine's Day 1999. Marshall and Piven had an interesting chemistry, and the actress gave a likable performance as the strong-willed but conflicted character. The following season, she could be seen on David E Kelley's "Snoops" (ABC, 1999-2000), playing a police detective turned P.I. alongside Gina Gershon and Paula Jai Parker in this quirky and promising comedy-infused crime drama.
Like many actors, Marshall began her film career in the horror genre, appearing in the uninspired sequels "Hellraiser III: Hell on Earth" (1992). and "Warlock: The Armageddon" (1993) before landing the plum role of Peter Weller's mistress in the satire "The New Age" (1994). She followed up with an appearance as Robert Duvall's daughter in the heartwarming, racially-themed feature "A Family Thing" (1996), and was cast as the daughter of Bette Midler and Dennis Farina in "That Old Feeling" (1997). Midler chose Marshall for the role of a bride-to-be whose wedding brings together her divorced parents after admiring her performance on the famed "Seinfeld" episode. She was next featured in the violent 1998 independent "Thursday", as the wife of a reformed drug dealer (Thomas Jane) whose past catches up with him.