Her paternal grandmother established and developed table tennis as a major sport in the mountainous municipality of Utuado, where her family grew up.

Melanie Díaz erupted onto the international arena by winning silver in the women's doubles alongside her sister Adriana during the 2014 Central American and Caribbean Games.

[11] Melanie Díaz first attained individual international recognition during the 2019 Pan American Games in Lima, where she was seeded #6 in the women category.

[12] She helped win the first Pan American Table Tennis gold for Puerto Rico when playing at the Women's doubles beside her sister Adriana.

Because of her playing skills in this match, international press nicknamed the female players of the Puerto Rican team as the "comeback kids.