Melissa grew up in Sayville, New York. Her acting career started at the age of four when she did a commercial for a bathtub toy called "Splashy". Her mother, Paula Hart, has been her agent from the beginning. Melissa has five younger sisters, Trisha, Elizabeth, Emily, Alexandra and Samantha, and one younger brother, Brian. All but the youngest sibling, Samantha, have been "in the business" in some capacity; Elizabeth, Emily and Brian have appeared on Melissa's current TV series, "Sabrina, the Teenage Witch".

Melissa performed in two plays as the youngest member of New York's Circle Repertory Lab Company: "Beside Herself" in 1989 (starring Lois Smith and William Hurt) and "Imagining Brad" in 1990.

She was also in the National Actors Theatre production of "The Crucible" on Broadway with Martin Sheen (as understudy to three of the children in the play). Melissa cites Shirley Temple and Audrey Hepburn as early acting inspirations.

She still collects Shirley Temple memorabilia. For the past few years, she has been juggling acting and attending New York University. She's now living in the Los Angeles area, starring in the ABC TV series "Sabrina, the Teenage Witch" (1996), which is produced by Hartbreak Films, the production company run by her and her mother.