She is best known for her roles in the telenovela Pobre Diabla and the films Captain Pantoja and the Special Services and Love in the Time of Cholera.

After her parents divorced she lived with her mother and two older sisters (one of whom is actress Lorna Paz).

Cepeda got a role in the soap opera Las Juanas, getting the attention of some TV producers who offered her jobs in prime time shows, such as the leading role in Luz Maria (1998), co-starring Christian Meier and Rosalinda Serfaty, and that as Fiorella Morelli Flores de Mejía Guzmán in Pobre Diabla (2000), opposite Salvador del Solar and Santiago Magill.

In the cinematic world, Peruvian director Francisco Lombardi convinced her to portray a prostitute called "La Colombiana" in Pantaleón y las Visitadoras (released in English as Captain Pantoja and the Special Services).

In 2021, she voiced Julieta Madrigal in the English, Spanish and Italian language versions of the Disney animated musical film Encanto.