Gretel started playing sports at the age of five, in a regular athletic school near her home. One day, she came to the gym and asked the coach to check her abilities, and the girl was immediately accepted. Soon she took part in the first competitions, after which she was invited to the sports academy. At the age of nine, Gretel entered the national school of gymnastics in Cuba.

In 2019, a month before the Pan American Games in Lima, the gymnast underwent surgery on her leg. She had very little time to recover. Despite this, she was able to become a finalist in the hoop exercises and placed fourth.