Witt made inroads on the big screen with a part in Mike Figgis' "Liebestraum" (1991) that also showcased her musical talent: she performed the Liszt tune that titled the feature in a dream sequence. Next up was a role in the ensemble drama "Bodies, Rest & Motion" (1993), which was followed by a roundly acclaimed performance in the independent feature "Fun" (1994) as Bonnie, a teenage girl who solidifies her bond with a new friend and plays out their ecstatic union by joining the girl in a senseless murder of an elderly woman. Witt shone in the chilling film, and her multifaceted performance brought such life to Bonnie that the character was oddly sympathetic. The actress' work in "Fun" earned her recognition in the form of an award from the Sundance Film Festival and also landed her a role as a lesbian witch opposite Madonna in 1995's "Four Rooms".
By now a familiar face in American homes due to her regular stint on "Cybill", Witt set out to prove her versatility and took a role in "Mr. Holland's Opus" (1995), playing Gertrude Lang, a shy, awkward clarinet student under the tutelage of composer turned reluctant instructor Glenn Holland (Richard Dreyfuss). Dedicated to her craft, Witt learned to play the clarinet in order to realistically represent her character. A starring role as a college student trying to stop a mysterious series of related campus murders in the 1998 horror thriller "Urban Legend" was preceded by a turn as the teenage daughter of a pro-life couple in 1996's "Citizen Ruth".
More TV work followed for the young actress, who was joined in a love triangle with Sela Ward and Timothy Hutton in the 1999 CBS TV-movie "Passion's Way", an early 1900s set adaptation of Edith Wharton's "The Reef". She incorporated her musical and acting talents lensing a role as a discouraged young concert pianist in "Playing Mona Lisa" (lensed 1999). A guest role as an opportunistic film development executive on a 2000 episode of HBO's popular series "The Sopranos" brought Witt back into the limelight, and a nude love scene revealed more of the actress than audiences had seen before. She next teamed up with John Waters for a role as a young porn actress in "Cecil B. Demented" (2000) and appeared in a recurring role on the FOX legal dramedy "Ally McBeal," tormenting Richard Fish (Greg Germann). Taking steps to graduate to roles in A-list films, Witt took a small supporting role opposite Tom Cruise in director Cameron Crowe's reality-bending "Vanilla Sky" (2001) and next co-starred as Hugh Grant's girlfriend and Sandra Bullock's romantic rival in the frothy comedy "Two Weeks Notice" (2002). She continued to turn in finely etched supporting turns on the big screen, playing one of Joan Allen's troublesome daughters in "The Upside of Anger" (2005) and mistress of Queen Latifah's antogonist (Timothy Hutton) who has a sympathetic side in the escapist confection "Last Holiday" (2006).