The news "really hit me hard," says Tavarez.
Her struggle also struck a chord with Alicia Keys and Rihanna. The singers, who both started their careers when they were young, decided to help get the word out that Tavarez needs a bone marrow transplant to live.
Keys says she was touched when she visited Tavarez on July 2 in the Long Island hospital where she receives daily chemotherapy treatments.
"For her, the sky is the limit, but now she's fighting for her life," the mom-to-be, who is asking fans to become donors, tells PEOPLE.
Keys hopes Tavarez and other patients like her to have the chance to "grow up to live their dreams."
Rihanna seconds that sentiment. "[Tavarez] should be performing on Broadway, but is confined to her bed, fighting for her life," Rihanna tells PEOPLE. "She needs to find a bone marrow donor to survive. I urge all my fans to register [as donors]. It's the most beautiful thing someone could do, to give the gift of life."
To become a donor visit DKMS Americas or The National Marrow Donor Program, which operates the national registry.