04/20/2009 at 01:00 AM EDT
flew into Manhattan on April 2 to visit 6-year-old Jasmina Anema at NYU Medical Center, the plan was to spend a quiet hour with the leukemia patient, who is awaiting a bone marrow transplant. But mix a mutual case of love-at-first-sight with a giggly dose of girls-just-want-to-have-fun, and before they knew it three hours had flown by. Rihanna
, who arrived toting a gift bag of cosmetics, gave Jasmina a princess makeover and manicure. The little girl offered a homemade drawing of the R&B star, a tour of her toys—her stuffed dog Jackie, like Jasmina, has an IV line for chemotherapy treatments—and a performance of her best dance moves. "She is such a little diva!" says a smitten Rihanna
. "It breaks my heart to see her go through this."
After learning of Jasmina's battle with NK-cell leukemia, Rihanna
, 21, asked People.com readers to register with DKMS Americas, a bone marrow donor registry (dkmsamericas.org). Her February appeal drew some 4,000 new donors—but none matched Jasmina. Now Rihanna
, spending time apart from Chris Brown, 19 (who pled not guilty April 6 to charges that he assaulted her), is seeking more donors. "As a little girl, I believed my mama's kisses made me get well," she says. "Instead of one kiss, Jasmina needs one perfect donor match."