Bay Shore teen Melina Mazzie’s wish came true six years ago, when a bone-marrow transplant from her brother helped her beat a blood disease.

In the spring, she’ll get a second wish: a visit to the Bahamas, courtesy of Make-A-Wish.

For now, she’s returning the favor to the nonprofit that helps grant such wishes to children with life-threatening illnesses.

Mazzie, 17, spent the last week collecting more than 13,000 letters to Santa Claus for Macy’s “Believe” campaign, which will donate $1 to the Make-A-Wish Foundation for every letter collected, up to $1 million.

Macy’s and Make-A-Wish of Suffolk County surprised Mazzie by honoring her Friday, as part of the Macy’s Believe Day event at South Shore Mall in Bay Shore on Friday afternoon.

Mazzie and her parents arrived by limo to the department store to find a band, dancers and podium, where Make-A-Wish and Macy’s officials honored the teen. She and her friends and family brought all 13,000 letters in boxes with wrapping paper as the crowd cheered.

They worked quickly to put them all into the big red mailbox Macy’s puts out for the campaign.

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“My journey has taught me so much it showed me the amazing friends and family I have around me,” Mazzie said. “Today isn’t about me, it’s about all the other kids fighting for their lives every day.”

In August 2010, Mazzie went to her family pediatrician for a simple checkup two weeks before her 11th birthday.

Her doctor was concerned about some blood test results and sent her to a specialist, who said Mazzie had aplastic anemia, a disease that was causing her body to shut down, and would need a bone-marrow transplant.

Her older brother Ryan Mazzie gave up his freshman year of high school football to donate the marrow, and Mazzie had a successful transplant later that year.

Mazzie also takes medication for another condition that makes her susceptible to strokes.

With her health under control, Make-A-Wish told the Mazzie family earlier this year they were granting Melina’s wish to visit the Atlantis resort in the Bahamas. The family will travel there next year.

But before even taking her trip, Mazzie wanted to give back, impressing Make-A-Wish officials. Karine Hollander, Suffolk Make-A-Wish CEO, said Mazzie’s efforts will help fund several wishes for other children.

“This helps them get their childhood back,” Hollander said. “The wish melts away some of that anxiety and some of that dread.”

A large chunk of the letters came from the Bay Shore school district.

Mazzie collected more than 4,800 letters from Bay Shore schools, with the help of her family and the district, which has 6,000 students.

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Krystyna Baumgartner, a district spokeswoman, said district officials were eager to help out when Mazzie, a senior at Bay Shore High School, and her father approached them with the idea. Make-A-Wish had also separately reached out.

“Everyone really rallied and said we need to do this for her,” Baumgartner said.

The response was better than she could have hoped for, Mazzie said, and she’s happy the letters can help other kids facing life-threatening illnesses.

“Make-A-Wish made my wish come true,” she said. “I wanted to give back.”