Scott was born Melody Ann Thomas in Los Angeles, California. Her first film credit was as a child actress in the 1964 Alfred Hitchcock movie, Marnie (1964). After bit parts in movies in the mid-'70s (most notably in John Wayne's final film, The Shootist (1976)), she was offered bit parts on nighttime series, such as The Waltons (1971), The Rockford Files (1974) and Charlie's Angels (1976).

In 1979, at the age of 23, she began playing the part of stripper "Nikki Reed" on the daytime serial, The Young and the Restless (1973), choosing the part over a sitcom pilot that, in the end, was not picked up. She was a replacement for the previous Nikki, who had lasted six months. Over time, her character reformed and became an important part of Genoa City society, as she married "Victor Newman" (Eric Braeden). Scott has said, "It's a miracle for an actor to have a job last 28 years", although she finds it frustrating to go through periods when she doesn't have a storyline. In 1987, she was offered to play the role of "Taylor Hughes" on As the World Turns (1956), but turned the offer down.

Scott was parodied in the satire publication, "The Onion", in 1999, in which a picture was edited to show her holding a Daytime Emmy (that year, Susan Lucci won the Emmy after 19 nominations). The caption read "Awards Given Out Randomly To Skinny Blonde Women". She appeared on various game shows over the years, including Family Feud (1976) (with various "Young and the Restless" co-stars), The $10,000 Pyramid (1973), Body Language (1984) and Match Game (1990).