"Kelly made me feel like a princess," Jasmina told PEOPLE Wednesday. "She made me feel so special."
Rowland had as much fun as Jasmina, who has a rare and deadly form of leukemia. "She made my day, to be quite honest," Rowland told PEOPLE. "It felt like a slumber party. She's so precious. She has such a beautiful spirit."
The former Destiny's Child star spent more than two hours with Jasmina and her best friend, Isabelle Huurman, 5. The trio frosted cupcakes, named Jasmina's new stuffed dog, Jazzilicous, and talked about The Little Mermaid's Ariel. "I'm 28 and I still love mermaids," Rowland told Jasmina, who was dressed in a tutu for her birthday bash.
Private PerformanceMouth sores from Jasmina's chemotherapy treatments made it hard for her to talk, but she did lots of smiling. "She was over the moon when Kelly sang to her," Jasmina's mom, Theodora Anema, told PEOPLE. "Kelly was so sweet. Jasmina loved her."
Jasmina, who used to have long braids, lost her hair because of her chemotherapy treatments. But the "hair fairy" left $108 under her pillow – one for each braid – which made her "so happy," says her mom.
What made Anema happy was when Rowland registered Wednesday as a donor by swabbing her cheek. "I loved making Jasmina feel like a princess for a day," says Rowland. "But when I heard about Jasmina, the first thing I thought of was, 'Maybe I could be a match for her.' I was praying about it afterward. You never know why you cross paths with someone. I encourage everyone to come out (to become donors).
Rihanna Wants to HelpMeanwhile Rihanna, who first got the word out about Jasmina last month, was "deeply moved" when she recently learned that more than 3,000 people responded to her Feb. 7 call on PEOPLE.com to help Jasmina find a bone marrow donor, according to Theadora.
New York Knicks' stars Chris Wilcox and Tyson Chandler are also helping, says Katharina Harf of DKMS, the world's largest nonprofit marrow donor center.
Wilcox, who recently visited Jasmina at the hospital, said, "I just can't bear to see a 5-year-old who literally would die if we don't find her a match soon."
For more information, contact DKMS at (866) 340-3567 or visit OneForJasmina.com. To learn more about living with and treating leukemia, visit Health.com.
Reporting By KRISTEN MASCIA