Mitchell made her television debut at age nine in "Children of the Bride" (1990), a CBS movie about an older woman (Rue McClanahan) who marries a younger man, much to the concern of her grown children. The young actress played Jersey Becker, one of the woman's grandchildren; a role she reprised in two subsequent sequels, "Baby of the Bride" (1991) and "Daughter of the Bride" (1993). Between the second and third installments of this series of TV-movies she had a turn in the 1992 CBS miniseries "Sinatra," playing the young incarnation of his eldest daughter Nancy in this look at the legendary entertainer's life.
In 1993, Mitchell guested on the reality-based anthology series "FBI: The Untold Stories" (ABC) and appeared from 1993-94 in three episodes of "Phenom" (also ABC), playing a classmate of the titular school-aged tennis champion. After making her film debut in the direct-to-video release "A Killing Obsession" (1994), the youngster landed a guest spot on Fox's "Melrose Place" and the next year, appeared again on that network in the sci-fi TV-movie "White Dwarf." 1996 proved a milestone year for the young actress: It was then that she landed the role of Lucy Camden on "7th Heaven" and played a supporting role in her first big screen outing, the supernatural sequel "The Crow: City of Angels."