Marrero turned professional in 1998. At the 2000 French Open, she reached the quarterfinals as a qualifier. In the second round, Marrero defeated Dominique Van Roost, who defeated number two seed Lindsay Davenport in the first round. Reaching the fourth round, she defeated Paraguay's Rossana de los Ríos in three sets. It was the first time in French Open history that two qualifiers met in the fourth round. In the quarterfinals, Marrero was defeated by eventual runner-up Conchita Martínez, 7–6, 6–1. At the 2001 French Open, she lost in the third round to Kim Clijsters, who finished runner-up.