Reis was born in Macau which was then a Portuguese colony. Reis is of mixed ancestry as her father is Portuguese and her mother is Chinese. Michelle maintains, however, that she considers herself Chinese as that was the only culture and language she grew up familiar with. Reis attended Maryknoll Convent School, and matriculated from St. Paul's Secondary School.

Reis started modelling at the age of 14. She first came to fame when she won the 1988 Miss Hong Kong Pageant at the age 18. Reis was also the first Miss Chinese International in the same year. Following her Miss Chinese International crowning, she went on to participate in the Miss World 1988 pageant, where she promoted the image of Hong Kong. She almost made the top 10, almost making it by a fraction of a score. She was then suppose to compete in the Miss Universe 1989 pageant but withdrew due to health problems.

Reis started to build a career within the entertainment industry in the 1990s. She starred in commercials eventually leading to movies. She has also appeared in music videos and TVB television episodes.