Avalanna had nicknamed herself 'Mrs Bieber' after meeting her idol in February. The 18-year-old 'Boyfriend' hitmaker took to Facebook and Twitter to pay tribute to his greatest fan, reported Radar online.
"Just got the worst news ever. One of the greatest spirits I have ever known is gone. Please pray for her family and for her. RIP Avalanna," he posted.
Devastated Biber grew close to his six-year-old fan, who was battling a rare and aggressive form of cancer, after flying to New York City to meet her and her mother for an extra special Valentine's Day date in February.
Biber became aware of Avalanna's desire to meet him following a social media campaign called 'Get Avalanna to Meet Justin Bieber' calling on him to grant the sick little girl's biggest wish.
Bieber was instantly touched after first meeting Avalanna in February.
He initially spent almost two hours playing with the little girl and returned to visit her several times before her death.
Avalanna also became actress Jessica Biel's 'hero' after meeting they met at a 'Stand Up To Cancer' fundraising event earlier this month.
