Corretjer dreamed about being a singer since she was little. Things began to fall in place for her when she was hired, at the age of 14, to host a tv show named La Nueva Ola (The New Wave, not to be confused with the Nueva Ola movement of the 1960s that produced such singers as Chucho Avellanet, Lucecita Benitez, Yolandita Monge, Ednita Nazario and Charlie Robles). With La Nueva Ola, she became a famous face in Puerto Rico.
When she was 21, she released the album Sola (Alone), which sent three of her songs to the Billboard lists. In 1997, she released her second album, Emociones (Emotions). With this second album, she toured places in South America, and later, she went to France to record a video for her song, Me Equivoque (I was wrong). Her third album, 1998's Amar es un Juego garnered her a golden album in Puerto Rico, her song De Hoy en Adelante (From Today On) staying on the Billboard charts for six weeks.
By 1999, there was rumors of her and De La Hoya dating. Before his fight with Felix Trinidad, he sent her a special greeting through the Puerto Rican press, describing her as his special friend.
By 2000, they admitted that they were dating. In 2001, they got married in San Juan, in what magazines like Vea and Teve-Guia described as a ridiculous and exaggerated ceremony, because they used quilts to block themselves from the press photographer's cameras, and their security did not allow press access to the event.
In 2003, they travelled to Argentina to act together in one of Millie's videos.
Millie appears on the cover of the September 2003 version of the Cosmopolitan magazine, talking about life with De La Hoya and announcing her new cd, Millie. The magazine says, in part, that Corretjer is attempting to become the Hispanic version of Shania Twain in her new work, also saying that she will be singing a Spanish version of country music.
Corretjer and actress Adamari Lopez have kept a public friendship since they were teenagers. And since she married De La Hoya, she has been able to become acquainted with such people as Sylvester Stallone and other Hollywood personalities. At a De La Hoya produced boxing undercard for HBO Latino in Miami, Corretjer and De La Hoya were seen talking with Stallone.