RIHANNA HELPS N.Y.C MOM FIND BONE MARROW DONOR

It's been a busy week for Rihanna, but when the Grammy-winning singer learned about a leukemia-stricken New York City mom of two who desperately needs a marrow transplant, she immediately stepped forward to help.

"When I heard about Lisa [Gershowitz Flynn]'s plight, my heart broke," Rihanna tells PEOPLE exclusively. "I said, ‘I need to get the word out about Lisa right away.' "

Besides scooping up her first Grammy and performing at the Brit Awards, the sultry 20-year-old singer returned to her native Barbados, where she has been named an honorary cultural ambassador.

Specifically, Rihanna is working with DKMS – the world's largest non-profit marrow donor center to help raise awareness for the need for people to come forward to become donors.

"I think DKMS is an incredible charity because you can really see the results," says Rihanna, who performed at the DKMS Linked Against Leukemia gala last May for free.

She adds: "My own charity, Believe, works specifically with children in need [and with children with leukemia]. Children need their mothers more than anything else in the world. Lisa has two children. My charity will continue to work with DKMS, because in finding a way to save Lisa's life, we will in turn be saving her children's lives."

Flynn, 41, is blown away that Rihanna is taking time to try to find a donor match for her and countless others who may die if they don't get one.

"For Rihanna to even be thinking about helping others and putting herself out there when she is so busy with her career is tremendous," says Flynn, the mother of Michael, 5, and Alexandra, 3, who learned she has an aggressive form of cancer called Acute Myelogenous Leukemia the day after Thanksgiving. Doctors told her she has four to six weeks to find a life-saving donor match.


Saving Lives
"Only two out of ten patients go into transplant, which means we need many, many more donors ... If we can find a match for Lisa, she can be saved. This is her only chance," says Katharina Harf, whose dad, Peter started DKMS in Germany in 1990 when he was desperately trying to find a donor for his wife and her mother, Mechtild, who was diagnosed with acute leukemia.

For Flynn, Jews of European (Ashkenazi) descent are the best candidates for a match. But anyone from 18 to 55 years old can be tested as a match for Flynn or thousands of others in need.

Getting tested is easy. Test results from a cheek swab are sent to a national bone-marrow registry. If the marrow is a match, donors undergo a minor outpatient surgery – to extract healthy stem cells to replace the patient's unhealthy cells.