Pop/R&B sensation Rihanna, who was just named honorary cultural ambassador of Barbados, has launched an appeal for a bone marrow donor with DKMS, a non-profit international donor network, to try to find a donor for Lisa Gershowitz Flynn.

Rihanna was compelled to help the 41-year-old mother of two, who's battling leukemia, when she heard Flynn's story. "When I heard about Lisa's plight, my heart broke," the singer told PEOPLE. "I said, 'I need to get the word out about Lisa right away.'"