In 2004, she started working at Caracol Radio and participated in various broadcasts for the network, among them Los 40 Principales, in which she was part of the morning program A Despertar.

In October of that year, Fonseca replaced the presenter and singer Adriana Tono [es] in the entertainment section of the news broadcast Caracol Noticias.

She made special coverage of beauty contests and fairs in Colombia and was nominated by TV y Novelas magazine as best entertainment presenter for her work at Caracol Noticias.

That year, she was the TV host for the program 13 Pasos for the Cosmopolitan channel, where she began a relationship with the Mexican actor Mark Tacher; they were married 2010 and divorced in 2011.

[6] In 2011, she was in a show called Los Originales produced by the broadcasting station La X of the Radial Todelar network along with Jaime Sánchez Cristo [es] and his crew.

In addition to being a presenter and host for special events, Fonseca has been spokesperson for several brands[7] such as Huggies, Mother Care, Pepa Pombo, Amelia Toro, Pink Filosofy, Apple, Almacenes Éxito, UNE, Pantene, Loreal, Despegar.com [es], BlackBerry, Seven-Seven Belier, Rowenta, Listerine, the Ministry of Labor and Adriana Arango.