Fidel Castro's niece Mariela Castro has lauded President Barack Obama's support for gay marriage.

“I think he's sincere and speaks from the heart,” Castro told roughly 200 people at the San Francisco Lesbian, Gay, Bisexual, Transgender Community Center on Wednesday.

“If we're not successful in changing these prejudices that bring stigma, discrimination, exclusion, we cannot advance as a new society,” she added.

The 50-year-old Castro, the daughter of Cuban President Raul Castro, heads the island nation's National Center for Sex Education and has advocated for gay rights, in particular the rights of transgender people.

(Related: Cuban government moves towards GLBT equality.)

Castro's visit to the U.S. was approved by the State Department. She will attend a conference on sexual diversity in Cuba at a conference of experts on Latin America. The decision to grant her a visa was attacked by several lawmakers, including New Jersey Senator Robert Menendez and Florida Senator Marco Rubio. Rubio called the decision “shameful” and a slap in the face to pro-democracy activists in Cuba, according to a press release.

Castro visited the United States in 2002 while George W. Bush was in office.

“I think [gay marriage is] something that he truly believes in … If I were a US citizen, I would vote for President Obama,” Castro said through an interpreter.

Castro heads to New York next week where she will participate in a conversation on international gay rights at the New York Public Library.