Little 'Mrs. Bieber,' 6, loses battle with brain cancer By Scott Stump, TODAY contributor The 6-year-old Boston girl best known as "Mrs. Bieber"" died Wednesday morning from the brain cancer she had battled for nearly her entire life. Justin Bieber and Avalanna Routh. Avalanna Routh struck up a friendship with Justin Bieber after he heard her story and about her love of his music. The two had a Valentine's Day date in New York in February after an online campaign and a report by WHDH came to Bieber's attention. In 2011, a Jimmy Fund benefit helped Routh "marry" Bieber in a pretend ceremony, earning her the moniker "Mrs. Bieber" and the popular #MrsBieber hashtag on Twitter. A post on her official Twitter account, which has 146,000 followers, reported the news of her death, which was confirmed by multiple media outlets. Our darling Avalanna went to Heaven this morning. Oh Avalanna, the brightest star -- you took our hearts with you, our greatest Love," the post read. On their date in February, Routh declared she had "Bieber fever,"" and playfully messed with the pop star's famous hairdo. The two played board games and signed autographs for each other. In June, Bieber brought Routh onstage at the Apollo Theater. "It's wonderful,"" Aileen Routh, Avalanna's mother, told NBC News after the date in February. "It was another fun moment."" "That was one of the best things I have ever done," Bieber tweeted after their date. Feeling really inspired right now.