She was discovered by an agent who saw her portray Flora in The Innocents, and Rhoda in The Bad Seed at local LA theatres.

[citation needed] After appearing in commercials, Wyss landed her first television role, recurring on Universal's When the Whistle Blows (1980) as Dolph Sweet's daughter.

In 1981, Wyss starred in the films This House Possessed and Force: Five, and guest-starred on episodes of the several television series, including Buck Rogers in the 25th Century, ABC Afterschool Specials, Jessica Novak, and Teachers Only.

In 1982, Wyss had a supporting role as high-school student Lisa in Amy Heckerling's teen comedy classic Fast Times at Ridgemont High, written by Cameron Crowe and featuring then-unknown actors Sean Penn, Phoebe Cates, Forest Whitaker, Jennifer Jason Leigh, and Nicolas Cage.

In 1983, Wyss appeared in the television films Lone Star, The Tom Swift and Linda Craig Mystery Hour, and A Killer in the Family.

The following year, Wyss starred with Loni Anderson in the television film My Mother's Secret Life before starring in Wes Craven's horror film A Nightmare on Elm Street (1984) as Tina Gray (the first person murdered onscreen by Freddy Krueger), along with Robert Englund, Heather Langenkamp, John Saxon, and Johnny Depp.

[citation needed] The following year, Wyss guest-starred in the television series Otherworld before starring in the films Silverado as Phoebe and Better Off Dead as Beth, who sank the main character into his depression by breaking up with him.

In 1991, Wyss reprised her role as Celia in Son of Darkness: To Die For II and starred alongside Mark Hamill in Black Magic Woman.