The daughter of Evelyn Avila and Santos Flores, she was born in Dangriga and was raised by her stepfather Bernard Rhys. She taught Spanish in high school in Dangriga. She went on to earn a BA in economics and political science from Hunter College in New York City. She returned to Belize and, in 1983, was named a justice of the peace. In 1988, Flores became the first woman mayor of Dangriga, serving two terms.
She was the Speaker of the House of Representatives from 1998 to 2001, and was President of the Senate from 2001 to 2003. In 2003, Flores was elected as representative for Dangriga; she was named Minister of Defence and National Emergency Management. In 2005, she was named Minister of Human Development and Women. After retiring from politics, she returned to teaching.
In 2013, she was named Woman of the Year by the United States Embassy in Belize.
- "Profile of new Speaker of House". News 5. September 9, 1998.
- "Sylvia Flores is Acting Prime Minister". 7 News Belize. July 29, 2005.
- "Hon. Sylvia Flores is Special Envoy's Trailblazer of the Week". The Guardian. April 30, 2013.