Belle was born to Cristina Gould, a Brazilian fashion designer and Jack Wesley Routh, a construction company owner and former country music composer. Belle was raised in a Catholic household. She attended the Católica Elementary School of São Paulo and then the Marlborough School, an all-girl high school in Los Angeles. She grew up speaking Portuguese. During her childhood, Belle would spend seasons in Santos, Brazil, where Cristina was born. She adopted many Brazilian habits, such as the taste for Brazilian telenovelas.